Pantothenamide analogues

Abstract

The present invention provides compounds that have antimalarial activity. More in particular, the present invention provides novel compounds that are analogues of pantothenamides. The pantothenamide analogues of this invention have particularly low IC.sub.50 values against the asexual blood stages and gametocytes of malaria parasites. Furthermore, the pantothenamide analogues of this invention are characterized by low hepatic metabolism. Therefore, pantothenamide analogues of the invention are particularly suitable for use in therapeutic and/or prophylactic treatment of protozoan infections in a human or animal subject in need thereof. The invention further provides pharmaceutical formulations comprising the pantothenamide analogues as well as the therapeutic and/or prophylactic uses of the pantothenamide analogues and pharmaceutical formulations comprising them.

Claims

1. A compound selected from the group consisting of the pantothenamide analogues represented by formula (I): ##STR00088## wherein ring E represents an optionally substituted phenyl ring or a pharmaceutically acceptable salt thereof.

2. The compound according to claim 1, wherein ring E represents phenyl, which may be substituted with 1-3 substituents independently selected from nitril and halo.

3. The compound according to claim 1, wherein ring E represents phenyl substituted with 1-3 substituents independently selected from chloro and fluoro.

4. The compound according to claim 1, wherein ring E represents phenyl substituted with three fluoro.

5. The compound according to claim 1, wherein ring E represents phenyl substituted with 1 nitril group.

6. The compound according to claim 1, which is selected from the compounds (A)-(J) and (A1)-(J1) having the structures as shown in the following table: TABLE-US-00006 No. Structure (A) (A1) (B) (B1) (C) (C1) (D) (D1) (E) (E1) (F) (F1) (G) (G1) (H) (H1) (I) (I1) (J) (J1)

7. The compound according to claim 6, selected from the compounds (A1), (B1), (C1) and (E1).

8. The compound according to claim 7, wherein the compound is (A1).

9. A pharmaceutical composition comprising an anti-malarial compound as defined in claim 1 and a pharmaceutically acceptable excipient.

10. The pharmaceutical composition according to claim 9, said composition comprising an additional anti-malarial agent.

11. The pharmaceutical composition according to claim 10, wherein said additional anti-malarial agent is selected from the groups consisting of atovaquone, chloroquine, hydroxychloroquine, primaquine, proguanil, quinidine, quinine, quinacrine, pyrimethamine-sulfadoxine, halofantrine, mefloquine, doxycycline, lumefantrine, amodiaquine, piperaquine, ferroquine, tafenoquine, arterolane, pyronaridine, artemisinin, artesunate, artemether, dihydroartemisinin, artenimol, Spiro[3H-indole-3,1′-[1H]pyrido[3,4-b]indol]-2(1H)-one, 5,7′-dichloro-6′-fluoro-2′,3′,4′,9′-tetrahydro-3′-methyl-,(1′R,3′S)-(CAS Registry Number: 1193314-23-6), Sulfur, [4-[[2-(1,1-difluoroethyl)-5-methyl[1,2,4]triazolo[1,5-a]pyrimidin-7-yl]amino]phenyl]pentafluoro-] (CAS Registry Number: 1282041-94-4), Morpholine,4-[2-(4-cis-dispiro [cyclohexane-1,3′-[1,2,4]trioxolane-5′,2″-tricyclo[3.3.1.1.sup.3,7]-decan]-4-ylphenoxy)ethyl]-(CAS Registry Number: 1029939-86-3), [3,3′-Bipyridin]-2-amine, 5-[4-(methylsulfonyl)phenyl]-6′-(trifluoromethyl)-(CAS Registry Number: 1314883-11-8), and Ethanone, 2-amino-1-[2-(4-fluorophenyl)-3-[(4-fluorophenyl)amino]-5,6-dihydroimidazo [1,2-a]pyrazin-7(8H)-yl]-(CAS Registry Number: 1261109-90-3).

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1. In vivo efficacy of pantothenamide analogues A1, B1, C1 and E1. In the graph the parasitemia (% infected red blood cells (RBC)) is plotted agains the number of days after infection. The arrow indicates the moment of administration of the respective treatments (vehicle comprising one of the respective pantothenamide analogues, vehicle without patothenamide analogue and chloroquine treatment).

EXAMPLES

(2) General Procedure for Amidation (General Procedure A)

(3) To a stirred solution of Amine (A1) (1 eqv) and Acid (A2) (1.2 eqv) in tetrahydrofuran (THF) (5 ml/mmol) were added 1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU) (1.5 eqv) and triethylamine (Et.sub.3N) (5 eqv) at 0° C. Reaction mixture was stirred at room temperature for 16 h. Reaction mixture was quenched with satd. sodium bicarbonate (NaHCO.sub.3) solution and extracted with ethyl acetate (EtOAc). The organic layer was washed with water, brine, dried over sodium sulfate (Na.sub.2SO.sub.4) and concentrated under reduced pressure. Crude was purified over a preparative thin layer chromatography (prep TLC) plate (methanol (MeOH)-dichloromethane (DCM)) to afford desired amide (A3).

(4) General Procedure for Acetonide Deprotection (General Procedure B)

(5) To a stirred solution of amide (A3) (1 eqv) in acetonitrile (CH.sub.3CN) (5 ml/mmol) was treated with bismuth(III)chloride (Bi(III)Cl.sub.3) (0.1 eqv) and H.sub.2O (0.04 ml/mmol). The reaction mixture was stirred at room temperature for 16 h. Reaction mass was concentrated under reduced pressure and purified over prep TLC (MeOH in DCM) to afford Final compound.

(6) ##STR00028##

Example 1: synthesis of (2R)-2,4-dihydroxy-3,3-dimethyl-N-[(2S)-2-[(2,4,5-trifluorophenyl)-formamido]propyl]butanamide (A1)

(7) ##STR00029## ##STR00030##

Synthesis of [(S)-2-(1,3-Dioxo-1,3-dihydro-isoindol-2-yl)-1-methyl-ethyl]-carbamic acid benzyl ester (3)

(8) ##STR00031##

(9) Procedure: To a stirred solution of ((S)-2-Hydroxy-1-methyl-ethyl)-carbamic acid benzyl ester (1) (50 g, 238.9 mmol) in dry THF (1500 mL) were added Phthalimide (2) (38.6 g, 262.8 mmol) and triphenylphosphine (PPh.sub.3) (68.9 g 262.8 mmol). Then diethylazodicarboxylate (DEAD) (41.2 mL, 262.8 mmol) was added drop wise at 0° C. Reaction was stirred at room temperature (RT) for 16 h. The reaction mixture was then concentrated and the residue was purified by column chromatography (silica gel, 100-200 mesh) using 20% EtOAc in hexane to afford [(S)-2-(1,3-Dioxo-1,3-dihydro-isoindol-2-yl)-1-methyl-ethyl]-carbamic acid benzyl ester (3) (53 g, 65.5%) as off white solid.

Synthesis of ((S)-2-Amino-1-methyl-ethyl)-carbamic acid benzyl ester (4)

(10) ##STR00032##

(11) Procedure: To a stirred solution of [(S)-2-(1,3-Dioxo-1,3-dihydro-isoindol-2-yl)-1-methyl-ethyl]-carbamic acid benzyl ester (3) (53 g, 47.7 mmol) in ethanol (EtOH) (450 mL) was added hydrazine hydrate (116.8 mL, 2406.4 mmol). Reaction mass was heated at 50° C. for 2 h. Reaction mass was cooled to RT, filtered and concentrated under reduced pressure. The resulting residue was again suspended in Et2O and filtered. The combined filtrates were concentrated under reduced pressure to afford ((S)-2-Amino-1-methyl-ethyl)-carbamic acid benzyl ester (4) (30 g, 96%) as colorless sticky gum.

Synthesis of [(S)-2-((R)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6)

(12) ##STR00033##

(13) Procedure: To a stirred solution of ((S)-2-Amino-1-methyl-ethyl)-carbamic acid benzyl ester (4) (26 g, 124.8 mmol) in EtOH (150 mL) were added D-(−)-Pantolactone (5) (48.7 g, 374.5 mmol) and Et3N (60.9 mL, 436.9 mmol). Reaction mixture was refluxed for 16 h. Reaction mixture was concentrated under reduced pressure to get crude mass which was purified by column chromatography (silica gel, 100-200 mesh) using 3% MeOH in DCM to afford [(S)-2-((R)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6) (31.2 g, 74%) as colorless sticky gum.

Synthesis of {(S)-1-Methyl-2-[((R)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7)

(14) ##STR00034##

(15) Procedure: To a stirred solution of [(S)-2-((R)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6) (31.2 g, 92.2 mmol) in DCM (270 mL) were added pyrdinium-p-toluenesulfonate (9.2 g, 36.2 mmol) and 2,2-dimethoxypropane (113.3 g, 922 mmol). Reaction mixture was stirred at RT for 16 h. Solvent was removed under reduced pressure and the crude product was purified by column chromatography (silica gel, 100-200 mesh) using 1% MeOH in DCM to afford {(S)-1-Methyl-2-[((R)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7) (22 g, 63%) as colorless sticky gum.

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (8)

(16) ##STR00035##

(17) Procedure: To a stirred solution of {(S)-1-Methyl-2-[((R)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7) (22 g, 58.1 mmol) in MeOH (160 mL) was degassed with nitrogen gas for 10 mins then 10% Pd/C (3 g) was added. Reaction mass was stirred at RT under hydrogen atmosphere (balloon pressure) for 3 h. Reaction mixture was filtered through celite and the filtrate was concentrated under reduced pressure to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (8) (14 g, 98.5%) as colorless sticky gum.

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10)

(18) ##STR00036##

(19) Procedure: Same as general procedure A with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (8) (5 g, 20.492 mmol) and 2,4,5-Trifluoro-benzoic acid (9) (3.609 g, 20.492 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10) as gum in 60.63% yield, 5 g.

Synthesis of (2R)-2,4-dihydroxy-3,3-dimethyl-N-[(2S)-2-[(2,4,5-trifluorophenyl) formamido]-propyl]butanamide (A1)

(20) ##STR00037##

(21) Procedure: Same as general procedure B with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10) (5 g, 12.425 mmol) to afford (2R)-2,4-dihydroxy-3,3-dimethyl-N-[(2S)-2-[(2,4,5-trifluorophenyl) formamido]propyl]-butanamide (A1) as light yellow sticky solid in 77.74% yield, 3.5 g. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.24 (d, J=7.56 Hz, 1H), 7.84 (t, J=5.88 Hz, 1H), 7.72-7.63 (m, 2H), 5.41 (d, J=5.48 Hz, 1H), 4.44 (t, J=5.58 Hz, 1H), 4.07-4.03 (m, 1H), 3.73 (d, J=5.48 Hz, 1H), 3.32-3.24 (m, 2H), 3.19-3.12 (m, 2H), 1.10 (d, J=6.64 Hz, 3H), 0.77 (s, 3H), 0.76 (s, 3H). LCMS (HCOOH:ACN): M+H=363, R.sub.t=1.46 min in 3 mins run.

Example 2: Synthesis of (2R)—N-[(2S)-2-[(5-cyano-2-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (B1)

(22) ##STR00038##

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(5-cyano-2-fluoro-benzoylamino)-propyl]-amide (3)

(23) ##STR00039##

(24) Procedure: Same as general procedure A with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (1) (4 g, 16.393 mmol) and 5-Cyano-2-fluoro-benzoic acid (2) (2.707 g, 16.393 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(5-cyano-2-fluoro-benzoylamino)-propyl]-amide (3) as gum in 56.57% yield, 3.63 g.

Synthesis of (2R)—N-[(2S)-2-[(5-cyano-2-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (B1)

(25) ##STR00040##

(26) Procedure: Same as general procedure B with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(5-cyano-2-fluoro-benzoylamino)-propyl]-amide (3) (3.63 g, 9.273 mmol) to afford (2R)—N-[(2S)-2-[(5-cyano-2-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethyl-butanamide (B1) as off white sticky solid in 73.66% yield, 2.4 g. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.39 (d, J=7.8 Hz, 1H), 8.08-8.02 (m, 2H), 7.84 (t, J=5.96 Hz, 1H), 7.54 (t, J=9.24 Hz, 1H), 5.41 (d, J=5.52 Hz, 1H), 4.45 (t, J=5.58 Hz, 1H), 4.08-4.02 (m, 1H), 3.74 (d, J=5.56 Hz, 1H), 3.31-3.23 (m, 2H), 3.20 (m, 2H), 1.10 (d, J=6.64 Hz, 3H), 0.78 (s, 3H), 0.77 (s, 3H). LCMS (HCOOH:ACN): M+H=352, R.sub.t=1.35 min in 3 mins run.

Example 3: synthesis of (2R)—N-[(2S)-2-[(3-cyanophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (C1)

(27) ##STR00041##

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3-cyano-benzoylaiamino)propyl]-amide (3)

(28) ##STR00042##

(29) Procedure: Same as general procedure A with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (1) (5 g, 20.463 mmol) and 3-Cyano-benzoic acid (2) (3.011 g, 20.463 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3-cyano-benzoylamino)-propyl]-amide (3) as gum in 50.32 yield, 4.2 g.

Synthesis of (2R)—N-[(2S)-2-[(3-cyanophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethyl-butanamide (C1)

(30) ##STR00043##

(31) Procedure: Same as general procedure B with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-(3-cyano-benzoylamino)-propyl-amide (3) (4.2 g, 11.246 mmol) to afford (2R)—N-[(2S)-2-[(3-cyanophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (C1) as off white solid in 82.68 (yield, 3.1 g. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.42 (d, J=7.6 Hz, 1H), 8.23 (s, 1H), 8.12 (d, J=6.64 Hz, 1H), 7.99 (d, J=7.44 Hz, 1H), 7.85 (brs, 1H), 7.68 (t, J=7.64 Hz, 1H), 5.39 (d, J=5.6 Hz, 1H), 4.43 (brs, 1H), 4.13-4.10 (m, 1H), 3.73 (d, J=5.6 Hz, 1H), 3.31-3.12 (m, 4H), 1.12 (d, J=6.36 Hz, 3H), 0.74 (s, 3H), 0.72 (s, 3H). LCMS (HCOOH:ACN): M+H=334, R.sub.t=1.42 min in 3 mins run.

Example 4: Synthesis of (2R)—N-[(?2S)-2-[(5-chloro-2,4-difluorophenyl) formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (D1)

(32) ##STR00044##

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(5-chloro-2,4-difluoro-benzoylamino)-propyl]-amide (3)

(33) ##STR00045##

(34) Procedure: Same as general procedure A with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (1) (2.3 g, 9.413 mmol) and 5-Chloro-2,4-difluoro-benzoic acid (2) (2.175 g, 11.296 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(5-chloro-2,4-difluoro-benzoylamino)-propyl]-amide (3) as gum in 91.31% yield, 3.6 g.

Synthesis of (2R)—N-[(2S)-2-[(5-chloro-2,4-difluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (D1)

(35) ##STR00046##

(36) Procedure: Same as general procedure B with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(5-chloro-2,4-difluoro-benzoylamino)-propyl]-amide (3) (3.2 g, 7.64 mmol) to afford (2R)—N-[(2S)-2-[(5-chloro-2,4-difluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (D1) as off white solid in 69.11% yield, 2 g. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.28 (d, J=7.56 Hz, 1H), 7.85-7.80 (m, 2H), 7.65 (t, J=9.78 Hz, 1H), 5.41 (d, J=5.52 Hz, 1H), 4.44 (t, J=5.56 Hz, 1H), 4.08-4.01 (m, 1H), 3.73 (d, J=5.52 Hz, 1H), 3.31-3.24 (m, 2H), 3.19-3.13 (m, 2H), 1.10 (d, J=6.64 Hz, 3H), 0.77 (s, 3H), 0.76 (s, 3H). LCMS (HCOOH:ACN): M+H=379, R.sub.t=1.43 min in 3 mins run.

Example 5: Synthesis of (2R)—N-[(2S)-2-[(3-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (E1)

(37) ##STR00047##

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3-fluoro-benzoylamino)-propyl]-amide (3)

(38) ##STR00048##

(39) Procedure: Same as general procedure A with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (1) (3 g, 12.295 mmol) and 3-Fluoro-benzoic acid (2) (1.723 g, 12.295 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3-fluoro-benzoylamino)-propyl]-amide (3) as gum in 77.69% yield, 3.5 g.

Synthesis of (2R)—N-[(2S)-2-[(3-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethyl-butanamide (E1)

(40) ##STR00049##

(41) Procedure: Same as general procedure B with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3-fluoro-benzoylamino)-propyl]-amide (3) (3.5 g, 9.552 mmol) to afford (2R)—N-[(2S)-2-[(3-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (E1) as off white solid in 63.56% yield, 2.2 g. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.31 (d, J=7.64 Hz, 1H), 7.85 (t, J=5.88 Hz, 1H), 7.66 (d, J=7.72 Hz, 1H), 7.61-7.58 (m, 1H), 7.53-7.48 (m, 1H), 7.39-7.34 (m, 1H), 5.40 (d, J=5.28 Hz, 1H), 4.44 (brs, 1H), 4.12-4.08 (m, 1H), 3.73 (d, J=5.28 Hz, 1H), 3.32-3.12 (m, 4H), 1.11 (d, J=6.64 Hz, 3H), 0.74 (s, 3H), 0.73 (s, 3H). LCMS (HCOOH:ACN). M+H=327, R.sub.t=1.45 min in 3 mins run.

Example 6: Synthesis of (2R)—N-[(2S)-2-[(3-chlorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (F1)

(42) ##STR00050##

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3-chloro-benzoylamino)-propyl]-amide (3)

(43) ##STR00051##

(44) Procedure: Same as general procedure A with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (1) (100 mg, 0.409 mmol) and 3-Chloro-benzoic acid (2) (76.89 mg, 0.491 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3-chloro-benzoylamino)-propyl]-amide (3) as gum in 95.72% yield, 150 mg.

Synthesis of (2R)—N-[(2S)-2-[(3-chlorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethyl-butanamide (F1)

(45) ##STR00052##

(46) Procedure: Same as general procedure B with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3-chloro-benzoylamino)-propyl]-amide (3) (150 mg, 0.392 mmol) to afford (2R)—N-[(2S)-2-[(3-chlorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (F1) as off white solid in 70.74% yield, 95 mg. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.35 (d, J=7.72 Hz, 1H), 7.85-7.81 (m, 2H), 7.77 (d, J=7.76 Hz, 1H), 7.58 (d, J=8 Hz, 1H), 7.49 (t, J=7.84 Hz, 1H), 5.40 (d, J=5.44 Hz, 1H), 4.43 (t, J=5.6 Hz, 1H), 4.11-4.06 (m, 1H), 3.73 (d, J=5.44 Hz, 1H), 3.33-3.24 (m, 2H), 3.21-3.11 (m, 2H), 1.11 (d, J=6.64 Hz, 3H), 0.75 (s, 3H), 0.73 (s, 3H). LCMS (HCOOH:ACN): M+H=343, R.sub.t=1.41 min in 3 mins run.

Example 7: Synthesis of (2R)—N-[(2S)-2-[(3-chloro-4-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (G1)

(47) ##STR00053##

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3-chloro-4-fluoro-benzoylamino)-propyl]-amide (3)

(48) ##STR00054##

(49) Procedure: Same as general procedure A with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (1) (100 mg, 0.409 mmol) and 3-Chloro-4-fluoro-benzoic acid (2) (71.415 mg, 0.491 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3-chloro-4-fluoro-benzoylamino)-propyl]-amide (3) as gum in 91.46% yield, 150 mg.

Synthesis of (2R)—N-[(2S)-2-[(3-chloro-4-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (G1)

(50) ##STR00055##

(51) Procedure: Same as general procedure B with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3-chloro-4-fluoro-benzoylamino)-propyl]-amide (3) (150 mg, 0.374 mmol) to afford (2R)—N-[(2S)-2-[(3-chloro-4-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethyl-butanamide (G1) as white solid in 37.04% yield, 50 mg. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.35 (d, J=7.64 Hz, 1H), 8.03 (d, J=5.68 Hz, 1H), 7.86-7.80 (m, 2H), 7.52 (t, J=8.84 Hz, 1H), 5.39 (d, J=5.24 Hz, 1H), 4.43 (t, J=5.22 Hz, 1H), 4.11-4.06 (m, 1H), 3.73 (d, J=5.24 Hz, 1H), 3.31-3.24 (m, 2H), 3.19-3.11 (m, 2H), 1.11 (d, J=6.64 Hz, 3H), 0.74 (s, 3H), 0.73 (s, 3H). LCMS (HCOOH:ACN): M+H=361, R.sub.t=1.43 min in 3 mins run.

Example 9: Synthesis of (2R)—N-[(2S)-2-[(3,4-difluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (H1)

(52) ##STR00056##

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3,4-difluoro-benzoylamino) propyl]-amide (3)

(53) ##STR00057##

(54) Procedure: Same as general procedure A with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (1) (75 mg, 0.307 mmol) and 3,4-Difluoro-benzoic acid (2) (48.6 mg, 0.307 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3,4-difluoro-benzoylamino)-propyl]-amide (3) as gum in 60.09% yield, 71 mg.

Synthesis of (2R)—N-[(2S)-2-[(3,4-difluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethyl-butanamide (H1)

(55) ##STR00058##

(56) Procedure: Same as general procedure B with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(3,4-difluoro-benzoylamino)-propyl]-amide (3) (71 mg, 0.185 mmol) to afford (2R)—N-[(2S)-2-[(3,4-difluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (H1) as off white sticky solid in 66.04% yield, 42 mg. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.32 (d, J=7.8 Hz, 1H), 7.90-7.80 (M, 2H), 7.69 (brs, 1H), 7.59-7.52 (m, 1H), 5.41 (d, J=5.36 Hz, 1H), 4.44 (brs, 1H), 4.10-4.06 (m, 1H), 3.72 (d, J=5.36 Hz, 1H), 3.28-3.10 (m, 4H), 1.11 (d, J=6.48 Hz, 3H), 0.73 (S, 6H). LCMS (HCOOH:ACN): M+H=345, R.sub.t=1.43 min in 3 mins run.

Example 10: Synthesis of (2R)—N-[(2S)-2-[(5-chloro-2-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (I1)

(57) ##STR00059##

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(5-chloro-2-fluoro-benzoylamino)-propyl]-amide (3)

(58) ##STR00060##

(59) Procedure: Same as general procedure A with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (1) (75 mg, 0.307 mmol) and 5-Chloro-2-fluoro-benzoic acid (2) (53.58 mg, 0.307 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(5-chloro-2-fluoro-benzoylamino)-propyl]-amide (3) as gum in 69.08% yield, 85 mg.

Synthesis of (2R)—N-[(2S)-2-[(5-chloro-2-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (I1)

(60) ##STR00061##

(61) Procedure: Same as general procedure B with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(5-chloro-2-fluoro-benzoylamino)-propyl]-amide (3) (80 mg, 0.2 mmol) to afford (2R)—N-[(2S)-2-[(5-chloro-2-fluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethyl-butanamide (I1) as colorless sticky gum in 53.13% yield, 40 mg. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.29 (d, J=6.88 Hz, 1H), 7.83 (brs, 1H), 7.60-7.58 (m, 2H), 7.35 (t, J=9.18 Hz, 1H), 5.42 (d, J=5 Hz, 1H), 4.45 (brs, 1H), 4.06-4.02 (m, 1H), 3.73 (d, J=5 Hz, 1H), 3.30-3.25 (m, 2H), 3.17-3.12 (m, 2H), 1.10 (d, J=6.4 Hz, 3H), 0.77 (s, 3H), 0.76 (s, 3H). LCMS (HCOOH:ACN): M+H=361, R.sub.t=1.43 min in 3 mins run.

Example 11: Synthesis of (2R)—N-[(2S)-2-[(2,5-difluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (J1)

(62) ##STR00062##

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(2,5-difluoro-benzoylamino)-propyl]-amide (3)

(63) ##STR00063##

(64) Procedure: Same as general procedure A with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (1) (75 mg, 0.307 mmol) and 2,5-Difluoro-benzoic acid (2) (48.53 mg, 0.307 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(2,5-difluoro-benzoylamino)-propyl]-amide (3) as gum in 67.8% yield, 80 mg.

Synthesis of (2R)—N-[(2S)-2-[(2,5-difluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide (J1)

(65) ##STR00064##

(66) Procedure: Same as general procedure B with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(2,5-difluoro-benzoylamino)-propyl]-amide (3) (70 mg, 0.182 mmol) to afford (2R)—N-[(2S)-2-[(2,5-difluorophenyl)formamido]propyl]-2,4-dihydroxy-3,3-dimethylbutanamide(J1) as colorless sticky gum in 61.34% yield, 45 mg. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.25 (d, J=7.16 Hz, 1H), 7.84 (t, J=5.92 Hz, 1H), 7.41-7.34 (m, 3H), 5.41 (d, J=5.48 Hz, 1H), 4.45 (t, J=5.6 Hz, 1H), 4.07-4.02 (m, 1H), 3.73 (d, J=5.48 Hz, 1H), 3.32-3.24 (m, 2H), 3.19-3.12 (m, 2H), 1.10 (d, J=6.6 Hz, 3H), 0.77 (s, 3H), 0.76 (s, 3H). LCMS (HCOOH:ACN): M+H=345, R.sub.t=1.37 min in 3 mins run.

Example 12: Synthesis of (2S)-2,4-dihydroxy-3,3-dimethyl-N-[(2R)-2-[(2,4,5-trifluorophenyl)-formamido]propyl]butanamide (A2)

(67) ##STR00065## ##STR00066##

Synthesis of [(R)-2-(1,3-Dioxo-1,3-dihydro-isoindol-2-yl)-1-methyl-ethyl]-carbamic acid benzyl ester (3)

(68) ##STR00067##

(69) Procedure: Same as [(S)-2-(1,3-Dioxo-1,3-dihydro-isoindol-2-yl)-1-methyl-ethyl]-carbamic acid benzyl ester (step 1 of A1 synthesis) with ((R)-2-Hydroxy-1-methyl-ethyl)-carbamic acid benzyl ester (1) (1.5 g, 7.168 mmol) to afford [(R)-2-(1,3-Dioxo-1,3-dihydro-isoindol-2-yl)-1-methyl-ethyl]-carbamic acid benzyl ester (3) as off white solid in 82.46% yield, 2 g.

Synthesis of ((R)-2-Amino-1-methyl-ethyl)-carbamic acid benzyl ester (4)

(70) ##STR00068##

(71) Procedure: Same as ((S)-2-Amino-1-methyl-ethyl)-carbamic acid benzyl ester (step 2 of A1 synthesis) with [(R)-2-(1,3-Dioxo-1,3-dihydro-isoindol-2-yl)-1-methyl-ethyl]-carbamic acid benzyl ester (3) (2.5 g, 7.388 mmol) to afford ((R)-2-Amino-1-methyl-ethyl)-carbamic acid benzyl ester (4) as colorless gum in 97.49% yield, 1.5 g.

Synthesis of [(R)-2-((S)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6**)

(72) ##STR00069##

(73) Procedure: Same as [(S)-2-((R)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (step 3 of A1 synthesis) with ((R)-2-Amino-1-methyl-ethyl)-carbamic acid benzyl ester (4) (300 mg, 1.441 mmol) and L-(+)-Pantolactone* (5) (375 mg, 2.881 mmol) to afford [(R)-2-((S)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6**) as colorless gum in 57.44% yield, 280 mg.

(74) * L-(+)-Pantolactone we received was not enantiomerically pure.

(75) ** The product 6 was obtained as a mixture (˜1:1) of [(R)-2-((S)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester and [(R)-2-((R)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester. The mixture was used and diastereomer separation performed on the final product.

Synthesis of {(R)-1-Methyl-2-[((S)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7**)

(76) ##STR00070##

(77) Procedure: Same as {(S)-1-Methyl-2-[((R)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (step 4 of A1 synthesis) with [(R)-2-((S)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6**) (330 mg, 2.881 mmol) to afford {(R)-1-Methyl-2-[((S)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7**) as colorless gum in 75.86% yield, 280 mg. ** Mixture of two diastereomers

Synthesis of (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((R)-2-amino-propyl)-amide (8**))

(78) ##STR00071##

(79) Procedure: Same as (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (step 5 of A1 synthesis) with {(R)-1-Methyl-2-[((S)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7**) (280 mg, 0.74 mmol) to afford (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((R)-2-amino-propyl)-amide (8**) as colorless gum in 99.56% yield, 180 mg. ** Mixture of two diastereomers

Synthesis of (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(R)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10**)

(80) ##STR00072##

(81) Procedure: Same as general procedure A with (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((R)-2-amino-propyl)-amide (8**) (180 mg, 0.737 mmol) and 2,4,5-Trifluoro-benzoic acid (9) (129.75 mg, 0.737 mmol) to afford (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(R)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10**) as colorless gum in 94.44% yield, 280 mg. ** Mixture of two diastereomers Synthesis of (2S)-2,4-dihydroxy-3,3-dimethyl-N-[(2R)-2-[(2,4,5-trifluorophenyl) formamido]-propyl]butanamide (A2):

(82) ##STR00073##

(83) Procedure: Same as general procedure B with (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(R)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10**) (280 mg, 0.696 mmol) and final diastereomer separation by prep HPLC (Column Name: Chiralpak IC (4.6×250 mm), 5μ, ARD/K/7788, Mobile Phase: Hexane/EtOH/IPamine: 80/20/0.1, Flow Rate: 1.0 ml/min, Solubility: MeOH) afford (2S)-2,4-dihydroxy-3,3-dimethyl-N-[(2R)-2-[(2,4,5-trifluorophenyl)formamido]propyl]butanamide (A2) (faster moving fraction) as colorless gum in 13.88% yield, 35 mg. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.24 (d, J=7.56 Hz, 1H), 7.84 (t, J=5.88 Hz, 1H), 7.72-7.63 (m, 2H), 5.41 (d, J=5.48 Hz, 1H), 4.44 (t, J=5.58 Hz, 1H), 4.07-4.03 (m, 1H), 3.73 (d, J=5.48 Hz, 1H), 3.32-3.24 (m, 2H), 3.19-3.12 (m, 2H), 1.10 (d, J=6.64 Hz, 3H), 0.77 (s, 3H), 0.76 (s, 3H). LCMS (HCOOH:ACN): M+H=363, R.sub.t=1.38 min in 3 mins run. ** Mixture of two diastereomers

Example 13: Synthesis of (2R)-2,4-dihydroxy-3,3-dimethyl-N-[(2R)-2-[(2,4,5-trifluorophenyl)-formamido]propyl]butanamide (A3)

(84) ##STR00074## ##STR00075##

Synthesis of [(R)-2-((R)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6)

(85) ##STR00076##

(86) Procedure: Same as [(S)-2-((R)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (step 3 of A1 synthesis) with ((R)-2-Amino-1-methyl-ethyl)-carbamic acid benzyl ester (4) (300 mg, 1.441 mmol) and D-(−)-Pantolactone (5) (375 mg, 2.881 mmol) to afford [(R)-2-((R)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6) as colorless gum in 47.18% yield, 230 mg.

Synthesis of {(R)-1-Methyl-2-[((R)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7)

(87) ##STR00077##

(88) Procedure: Same as {(S)-1-Methyl-2-[((R)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (step 4 of A1 synthesis) with [(R)-2-((R)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6) (240 mg, 0.709 mmol) to afford {(R)-1-Methyl-2-[((R)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7) as off white solid in 85.69% yield, 230 mg.

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((R)-2-amino-propyl)-amide (8)

(89) ##STR00078##

(90) Procedure: Same as (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (step 5 of A1 synthesis) with {(R)-1-Methyl-2-[((R)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7) (230 mg, 0.608 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((R)-2-amino-propyl)-amide (8) as colorless gum in 94.17% yield, 140 mg.

Synthesis of (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(R)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10)

(91) ##STR00079##

(92) Procedure: Same as general procedure A with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((R)-2-amino-propyl)-amide (8) (140 mg, 0.573 mmol) and 2,4,5-Trifluoro-benzoic acid (9) (100.917 mg, 0.573 mmol) to afford (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(R)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10) as colorless gum in 91.06% yield, 210 mg.

Synthesis of (2R)-2,4-dihydroxy-3,3-dimethyl-N-[(2R)-2-[(2,4,5-trifluorophenyl)formamido]-propyl]butanamide (A3)

(93) ##STR00080##

(94) Procedure: Same as general procedure B with (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(R)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10) (210 mg, 0.522 mmol) to afford (2R)-2,4-dihydroxy-3,3-dimethyl-N-[(2R)-2-[(2,4,5-trifluorophenyl)formamido]propyl]-butanamide (A3) as light brown sticky gum in 47.6% yield, 90 mg. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.23 (d, J=8 Hz, 1H), 7.83 (t, J=5.88 Hz, 1H), 7.70-7.64 (m, 2H), 5.42 (d, J=5.4 Hz, 1H), 4.45 (t, J=5.5 Hz, 1H), 4.04-4.00 (m, 1H), 3.72 (d, J=5.4 Hz, 1H), 3.31-3.26 (m, 2H), 3.16-3.06 (m, 2H), 1.09 (d, J=6.56 Hz, 3H), 0.79 (s, 3H), 0.75 (s, 3H). LCMS (HCOOH:ACN): M+H=363, R.sub.t=1.38 min in 3 mins run.

Example 14: Synthesis of (2S)-2,4-dihydroxy-3,3-dimethyl-N-[(2S)-2-[(2,4,5-trifluorophenyl)-formamido]propyl]butanamide (A4)

(95) ##STR00081## ##STR00082##

Synthesis of [(S)-2-((S)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6**)

(96) ##STR00083##

(97) Procedure: Same as [(S)-2-((R)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (step 3 of A1 synthesis) with ((S)-2-Amino-1-methyl-ethyl)-carbamic acid benzyl ester (4) (350 mg, 1.681 mmol) and L-(+)-Pantolactone* (5) (437.42 mg, 3.361 mmol) to afford [(S)-2-((S)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6**) as colorless gum in 45.72% yield, 260 mg. * L-(+)-Pantolactone turned out not to be enantiomerically pure. ** Product 6 was obtained as a mixture (˜1:1) of [(S)-2-((S)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester and [(S)-2-((R)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester. The mixture was used and diastereomers were separated from the end-product.

Synthesis of {(S)-1-Methyl-2-[((S)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7**)

(98) ##STR00084##

(99) Procedure: Same as {(S)-1-Methyl-2-[((R)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (step 4 of A1 synthesis) with [(S)-2-((S)-2,4-Dihydroxy-3,3-dimethyl-butyrylamino)-1-methyl-ethyl]-carbamic acid benzyl ester (6**) (260 mg, 0.768 mmol) to afford {(S)-1-Methyl-2-[((S)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7**) as colorless gum in 75.66% yield, 220 mg. ** Mixture of two diastereomers

Synthesis of (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (8**))

(100) ##STR00085##

(101) Procedure: Same as (R)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (step 5 of A1 synthesis) with {(S)-1-Methyl-2-[((S)-2,2,5,5-tetramethyl-[1,3]dioxane-4-carbonyl)-amino]-ethyl}-carbamic acid benzyl ester (7**) (220 mg, 0.582 mmol) to afford (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (8**) as colorless gum in 91.42% yield, 130 mg. ** Mixture of two diastereomers

Synthesis of (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10**)

(102) ##STR00086##

(103) Procedure: Same as general procedure A with (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid ((S)-2-amino-propyl)-amide (8**) (130 mg, 0.533 mmol) and 2,4,5-Trifluoro-benzoic acid (9) (93.77 mg, 0.533 mmol) to afford (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10**) as colorless gum in 88.62% yield, 190 mg. ** Mixture of two diastereomers

Synthesis of (2S)-2,4-dihydroxy-3,3-dimethyl-N-[(2S)-2-[(2,4,5-trifluorophenyl)formamido]-propyl]butanamide (A4))

(104) ##STR00087##

(105) Procedure: Same as general procedure B with (S)-2,2,5,5-Tetramethyl-[1,3]dioxane-4-carboxylic acid [(S)-2-(2,4,5-trifluoro-benzoylamino)-propyl]-amide (10**) (190 mg, 0.472 mmol) and final diastereomer separation by prep HPLC (Column Name: Chiralpak IC (4.6×250 mm), 5μ, ARD/K/7788, Mobile Phase: Hexane/EtOH/IPamine: 80/20/0.1, Flow Rate: 1.0 ml/min, Solubility: MeOH) afford (2S)-2,4-dihydroxy-3,3-dimethyl-N-[(2S)-2-[(2,4,5-trifluorophenyl)formamido]-propyl]butanamide (A4) (faster moving fraction) as colorless gum in 14.61% yield, 25 mg. .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 8.23 (d, J=8 Hz, 1H), 7.83 (t, J=5.88 Hz, 1H), 7.70-7.64 (m, 2H), 5.42 (d, J=5.4 Hz, 1H), 4.45 (t, J=5.5 Hz, 1H), 4.04-4.00 (m, 1H), 3.72 (d, J=5.4 Hz, 1H), 3.31-3.26 (m, 2H), 3.16-3.06 (m, 2H), 1.09 (d, J=6.56 Hz, 3H), 0.79 (s, 3H), 0.75 (s, 3H). LCMS (HCOOH:ACN): M+H=363, R.sub.t=1.38 min in 3 mins run.

Example 15: Antimalarial Activity

(106) Plasmodium falciparum strain NF54 was cultured in Roswell Park Memorial Institute (RPMI) 1640 medium supplemented with 25 mM NaHCO.sub.3, 10% human type A serum and 5% (v/v) human type 0 red blood cells (Sanquin, the Netherlands). Replication assays for asexual blood-stage parasites were performed by diluting parasites in RPMI1640 medium with 10% human serum to a parasitemia of 0.83% and a hematocrit of 3%. 30 μl of diluted parasites were combined with 30 μl of compound serially diluted in DMSO and RPMI1640 medium to reach a final DMSO concentration of 0.1% in a total assay volume of 60 μL. Following a 72 h incubation at 37° C., 3% O.sub.2, 4% CO.sub.2, 30 μL of diluted SYBR® Green reagent was added according to the instructions of the manufacturer (Life Technologies) and fluorescence intensity was quantified using a Biotek Synergy® 2 plate reader. Gametocyte viability assays were initiated by inoculating a culture flask with 1% asexual blood-stage parasites in 5% haematocrit in RPMI1640 medium with 10% human serum. From day 4 to day 9 after inoculation, cultures were treated with 50 mM N-acetylglucosamine to eliminate asexual blood-stage parasites. At day 11 post inoculation, gametocytes (predominantly stage IV) were isolated by Percoll® density gradient centrifugation. Gametocytes were seeded at a density of 5,000 cells/well in a 384 well plate and combined with compound diluted in DMSO and subsequently in RPMI1640 medium to reach a final DMSO concentration of 0.1% in a volume of 60 μL RPMI1640 medium with 10% human serum. Following a 72 h incubation at 37° C., 3% O.sub.2, 4% CO.sub.2, 30 μL of ONE-Glo® reagent (Promega) was added and luminescence was quantified using a Biotek Synergy 2 reader. IC.sub.50 values were derived by fitting a four parameter logistic regression model to the data using least squares to find the best fit. Resulting IC.sub.50 values against P. falciparum NF54 asexual blood stage parasites and gametocytes are presented in table 2.

Table 2

(107) Activities of pantothenamide analogues against P. falciparum asexual blood stage parasites and gametocytes. The table shows average IC50 values derived from at least two replicate experiments.

(108) TABLE-US-00002 antimalarial IC.sub.50 (nM) Compound asexual blood stages gametocytes A1 2.4 8.0 B1 6.2 21.4 C1 7.4 2.2 D1 2.3 0.4 E1 1.9 2.0 F1 2.1 0.4 G1 3.4 0.2

Example 16: Metabolic Stability in Human Primary Hepatocytes

(109) Metabolic stability of compounds of the invention was assessed in a hepatocyte relay assay. Human primary hepatocytes (Xenotech) were cultured in collagen coated 96-well plates in Williams E (Gibco® 32551087) supplemented with 1% PenStrep (Gibco 15140-122), 1% Fungizone® (Gibco 15290026), 10% heat-inactivated fetal bovine serum (hiFBS) (Gibco 10270-106), 0.1 IU/ml insulin (Sigma I2643) and 7 μM hydrocortisone hemisuccinate (Sigma H2270) at 37° C. and 5% CO.sub.2. Test compounds were added to a final concentration of 10 μM in 0.1 DMSO. Every 24 hours, the cell supernatant was transferred to freshly plated, metabolically full active cells. At regular time intervals, aliquots of supernatants were frozen for future analysis. At the end of the incubation, all samples were thawed and compound levels in time were determined by LC-MS analyses. Data were analysed by linear regression. Resulting clearance values and half-lifes are presented in table 3. The data show that all compounds tested show low clearance in human hepatocytes.

(110) Table 3—Metabolic stability of pantothenamide analogues in human primary cells as assessed in a relay assay. The table shows intrinsic clearance (Clint) expressed as μl/min/10.sup.6 cells and half-life expressed in minutes. Values indicate average values from two replicate experiments and their cognate standard deviations (s.d.).

(111) TABLE-US-00003 Clint (μl/min/ 10.sup.6 cells) T½ (mins) Compound average s.d. average s.d. A1 0.4 0.079486 3564.5 713.9024 B1 0.2 0.009849 6395.3 290.2712 C1 0.3 0.006448 5043.1 118.2598 E1 0.5 0.037744 2530.1 173.8748

Example 17: In Vivo Antimalarial Activity

(112) Reduction of existing parasitemia in vivo was investigated using a humanized mouse model for P. falciparum infection. Female NODscidIL2Rγnull mice were engrafted by daily intravenous injection of 0.6 ml of human blood for 11 days. Subsequently, mice were infected with P. falciparum strain Pf3D70087/N9 by injecting 2.10.sup.7 parasites in a volume of 0.2 ml. Four days post infection, mice were treated with a single 50 mg/kg dose of test compound. To this end, compounds were formulated in 70% Tween®-80 (d=1.08 g/ml) and 30% ethanol (d=0.81 g/ml), followed by a 10-fold dilution in H.sub.2O and administered by oral gavage. Parasitemia was followed by daily collection of 2 μl tail blood. The hematocrit was determined by fluorescence-activated cell sorting (FACS) and parasitemia by microscopy on >10,000 red blood cells. FIG. 1 shows the in vivo efficacy of pantothenamide analogues. The FIGURE shows parasitemia (% of infected human red blood cells) in time in a humanized mouse model for P. falciparum asexual blood stage infection. The compounds indicated at the legend were dosed as a single oral dose of 50 mg/kg at day 4 post infection (indicated by the arrow) and parasitemia was followed for another three days. The data shown in FIG. 1 indicate that all pantothenamide analogues tested show a dramatic reduction in blood stage parasitemia at a single oral dose of 50 mg/kg.

(113) Table 4—In vivo efficacy of pantothenamide analogues determined in female NODscidIL2Rγnull mice infected with P. falciparum strain Pf3D70087/N9. The table shows the log reduction in parasitemia.

(114) TABLE-US-00004 In vivo efficacy log reduction in parasitemia in Pf Compound SCID mouse at 50 mg/kg p.o. 1 × QD A1 >3 B1 2.4 C1 >3 E1 >3

Comparative Example

(115) A compound denominated MMV689258 was disclosed in WO2016/072854. For this compound metabolic stability and in vivo efficacy data have been generated following the same protocols as described in present examples 16 and 17 respectively. The results are summarized in table 5 below. As can be inferred from this data, the compound denominated MMV689258 has a metabolic stability substantially lower than the compounds of the invention and is substantially less efficacious in vivo.

(116) Table 5—Metabolic stability and in vivo efficacy of MMV689258. Metabolic stability was determined in human primary cells assessed in a relay assay. The table shows intrinsic clearance (Clint) expressed as μl/min/10.sup.6 cells and half-life expressed in minutes. In vivo efficacy was determined in female NODscidIL2Rγnull mice infected with P. falciparum strain Pf3D70087/N9. The table shows the log reduction in parasitemia.

(117) TABLE-US-00005 Metabolic stability in In vivo efficacy human hepatocytes log reduction in parasitemia Clint (μl/min/ T½ in Pf SCID mouse at Compound 10.sup.6 cells) (mins) 50 mg/kg p.o. 1 × QD MMV689258 0.8 1764.2 1.5