Synthesis of morin and morin derivatives

Abstract

The invention relates to a method for directly producing morin derivatives and high-purity morin of formula (I). The invention also relates to morin derivatives and high-purity morin that can be obtained using the claimed method. ##STR00001##

Claims

1. A method for producing a compound of formula (1) ##STR00012## comprising the following steps: i) acetylation of a compound of formula (4) ##STR00013## to form an acetophenone of formula (6) ##STR00014## ii) transforming the acetophenone of formula (6) with a compound of formula (7) under alkaline conditions ##STR00015## at room temperature to form a chalcone of formula (8) ##STR00016## iii) transforming the chalcone of formula (8) under oxidising conditions in an alkaline environment to form a flavonol of formula (9) ##STR00017## iv) and demethylation of the flavonol of formula (9), wherein R.sup.1, R.sup.2, R.sup.4, R.sup.5 and R.sup.8 are a branched or linear C.sub.1-C.sub.8-alkyl, NO.sub.2, SO.sub.3H, NX.sub.2, wherein X is ethyl gr methyl, CF.sub.3 or hydrogen, and R.sup.7 and R.sup.8 are independently of one another a methyl-, ethyl-, t-butyl-, benzyl-, methoxymethyl-, p-methoxybenzyl-, benzyloxymethyl-, triphenylmethyl-, tetrahydropyranyl- or allyl group.

2. The method according to claim 1, wherein R.sup.1, R.sup.2, R.sup.4, R.sup.5 and R.sup.6 are C.sub.1-C.sub.5-alkyl or hydrogen.

3. The method according to claim 1, wherein R.sup.1, R.sup.2, R.sup.4, R.sup.5 and R.sup.6 are C.sub.1-C.sub.3-alkyl or hydrogen.

4. The method according to claim 1, further comprising step (i-a): (i-a) methylation of a compound of formula (3) ##STR00018## under acidic conditions to form the compound of formula (4), wherein R.sup.1, R.sup.2, R.sup.4, R.sup.5 and R.sup.6 are defined as in claim 1, and wherein R.sup.3 is a branched or linear C.sub.1-C.sub.8-alkyl, NO.sub.2, SO.sub.3H, NX.sub.2, wherein X is ethyl or methyl, CF.sub.3 or hydrogen.

5. The method according to claim 4, wherein R.sup.3 is hydrogen.

6. The method according to claim 1, wherein R.sup.1, R.sup.2, R.sup.4, R.sup.5 and R.sup.6 are hydrogen.

7. The method according to claim 1, wherein, in step iii), the oxidising conditions are produced by means of tert-butylhydroperoxide and the alkaline environment is produced by means of an alkali hydroxide.

8. The method according to claim 1, wherein, in step ii), the alkaline conditions are produced by means of an alkali hydroxide and the reaction takes place at room temperature.

9. The method according to claim 1, wherein, in step i), the acetylation takes place by means of acetyl chloride in the presence of a Lewis acid and dichloromethane.

10. The method according to claim 1, wherein in, step (i-a), the acidic conditions are produced by means of an inorganic acid.

11. A method for the electrolytic deposition of tin or tin/lead on a metal sheet, such method comprising the addition of one or more compounds of formula (1) ##STR00019## wherein R.sup.1, R.sup.2, R.sup.4, R.sup.5 and R.sup.6 are a branched or linear C.sub.1-C.sub.8-alkyl, NO.sub.2, SO.sub.3, NX.sub.2, wherein X is ethyl or methyl, CF.sub.3 or hydrogen, to an electroplating bath comprising a tin or tin/lead electroplating solution and applying a current to the metal sheet, wherein the addition of the one or more compounds of formula (1) to the electroplating solution results in a tin or tin/lead layer obtained exhibiting 20% lower tin or tin/lead layer porosity when compared to such method wherein the one or more compounds of formula (1) were not added to the electroplating solution.

12. The method according to claim 11, wherein the tin or tin/lead layer obtained exhibits 35% lower tin or tin/lead layer porosity.

13. The method according to claim 11, wherein R.sup.1, R.sup.2, R.sup.4, R.sup.5 and R.sup.6 are C.sub.1-C.sub.5-alkyl or hydrogen.

14. The method according to claim 11, wherein R.sup.1, R.sup.2, R.sup.4, R.sup.5 and R.sup.6 are C.sub.1-C.sub.3-alkyl or hydrogen.

Description

EXAMPLE 1

Producing 3,5-dimethoxyphenol (4)

(1) Under an argon atmosphere, phloroglucinol (3) (80.0 g, 634 mmol, 1.0 eq.) was solubilised in methanol (400 mL). Slowly, sulfuric acid (95%, 46.3 mL, 825 mmol, 1.3 equivalent) was added dropwise, and the reaction mixture was stirred for 26 hrs at 80° C. under reflux. Subsequently, 10% aqueous potassium carbonate solution (800 mL) and toluol (300 mL) were added. After separating the phases, the aqueous solution was extracted twice with toluol (300 ml, respectively). The aqueous phase was brought with 2 M HCl solution to pH<2 and extracted three times with ethyl acetate (je 300 ml, respectively). The combined organic phases were dried over sodium sulphate, and the solvent removed in high vacuum. After purification by means of fractional distillation compound (4) (81.2 g, 527 mmol, 83%) was obtained as colourless oil. Additionally, it was possible to obtain by-product (5) (4.71 g, 28.0 mmol, 4.4%) as colourless oil, 3,5-Dimethoxyphenol (4): Boiling point: 139-141° C. (2.8 mbar). DC [Petrol ether/Ethyl acetate (2:1)]: R.sub.f=0.40. (400 MHz, CDCl.sub.3): δ=6.08 (t, J=2.2 Hz, 1H, 4-CH), 6.03 (d, J=2.2 Hz, 2H, 2-CH, 6-CH), 5.19 (s, 1H, OH), 3.75 (s, 6H, OCH.sub.3). .sup.13C-NMR (100 MHz, CDCl.sub.3): d=162.0 (2C, C.sub.Ph—OCH.sub.3), 157.7 (C.sub.Ph—OH), 94.6 (2C, C-2, C-6), 93.5 (C-4), 55.7 (2C, OCH.sub.3). IR (Diamant-ATR): {tilde over (V)}=3384 (m, br.), 3003 (w), 2942 (w), 2842 (w), 1595 (s), 1500 (m), 1458 (m), 1433 (m), 1342 (m), 1294 (m), 1 192 (s), 1 139 (s), 1052 (s), 992 (m), 973 (m), 924 (m), 818 (a), 679 (m). UV (MeOH): λ.sub.max (Ig ε)=267 (2.79), 206 (4.60). MS (EI): m/z (%)=69 [M-MeOC—CH—COH].sup.+ (18), 125 [M-COH].sup.+ (60), 154 [M].sup.+ (100).

(2) It was possible to obtain the product in a yield of 78%. This was mainly possible due to the second extraction of the aqueous phase after reducing the pH value, which results in an additional 23% yield of the product. Increasing the reaction time was necessary especially in larger batches; it was increased from 21 hrs at 500 mg batches to 30 hrs at 20 g batches. The characterisation analyses of the product met the expectations.

(3) During the reaction, two by-products were fond and isolated. One of them is the single-methylated 5-Methoxybenzol-1,3-diol, which was possible to be confirmed by .sup.1H-NMR and .sup.13C-NMR analyses. The yield was here at 15%. The other by-product is the thrice-methylated 3,5-Trimethoxybenzol, which occurred at a yield of 7%. .sup.1H-NMR and .sup.15C-NMR analyses were also able to confirm the structure. By-product 1,3,5-Trimethoxybenzol (5) [12]: yield: 7©, DC [Petrol ether/Ethyl acetate (2:1)]: R.sub.f=0.78. Boiling point: 135-137° C. (2.8 mbar). .sup.1H-NMR (400 MHz, CDCl.sub.3): d=6.09 (s, 3H, Ph-H), 3.77 (s, 9H, OCH.sub.3). .sup.13C-NMR (100 MHz, CDCl.sub.3): d=161.6 (3C, C.sub.Ph—OCH.sub.3), 92.9 (3C, Cp.sub.h), 55.3 (3C, OCH.sub.3). IR (Diamant-ATR): {tilde over (V)}=3075 (w), 3004 (m), 2963 (m), 2940 (m), 2839 (m), 1591 (s), 1480 (m), 1456 (s) 1423 (m), 1339(m), 1322 (m), 1252 (w), 1209 (a), 1 194 (m), 1 147 (a), 1064 (s), 1034 (a), 990 (m), 942 (m), 916 (m), 847 (s), 822 (s), 779 (s), 686 (s), 640 (m), 616 (m), 591 (m), 537 (m). UV (MeOH): λ.sub.max (Ig ε) 266 (2.62), 207 (4.47). MS (EI): m/z (%)=69 [M-MeOC—CH—COMe].sup.+ (83), 125 [M-COMe].sup.+ (100), 167 [M].sup.+ (100).

Example 2

Producing 1-(2-Hydroxy-4,6-dimethoxyphenyl)ethane-1-one (6)

(4) Under an argon atmosphere, boron trichloride (1 M in dichloromethane, 48.9 mL, 48.9 mmol, 1.0 eq.) was solubilised in dichloromethane (50 ml) and cooled to −10° C. 3,5-Dimethoxyphenol (4) (7.54 g, 48.9 mmol, 1.0 eq.), pre-solubilised in dichloromethane (25 mL), was added dropwise. The reaction mixture was brought to room temperature and stirred for 30 min. Subsequently, acetyl chloride (4.54 ml, 63.6 mmol, 1.3 eq.), pre-solubilised in dichloromethane (80 ml), was added dropwise within 15 min. The reaction mixture was stirred for 3 hrs under reflux. After cooling, the 1 M aqueous HCl solution (300 ml) was added. The phases were separated, and the aqueous phase extracted three times with ethyl acetate (200 ml, respectively). The combined organic phases were dried over sodium sulphate, and the solvent removed in high vacuum. After column-chromatographic cleaning on silica gel [Petrol ether/Ethyl acetate (2:1)] the acetophenone derivative (6) (7.38 g, 37.6 mmol, 77%) was obtained as colourless solid. DC [Petrol ether/Ethyl acetate (2:1)]: 0.73. Melting point: 79-82° C. .sup.1H-NMR (400 MHz, DMSO-d.sub.6): δ=14.03 (s, 1H, OH), 6.06 (d, J=2.4 Hz, 1H, 5-CH), 5.92 (d, J=2.4 Hz, 1H, 3-CH), 3.85 (s, 3H, o-Ph-OCH.sub.3), 3.82 (s, 3H, p-Ph-OCH.sub.3), 2.61 (s, 3H, 0=CCH.sub.3). .sup.13C-NMR (100 MHz, DMSO-d.sub.6): δ=203.2 (C=0), 167.6 (p-C.sub.Ph—OCH.sub.3), 166.1 (o-C.sub.Ph—OCH.sub.3), 162.9 (o-C.sub.Ph—OH), 106.0 (C.sub.Ph—C=0), 93.5 (C-5), 90.75 (C-3), 55.5 (2C, OCH.sub.3), 32.9 (CH.sub.3). IR (Diamant-ATR): v=3103 (w, br.), 3008 (w), 2945 (w, br.), 2849 (w, br.), 2705 (w, br.), 2599 (w, br.), 1613 (s), 1457 (m), 1441 (m), 1423 (m), 1389 (m), 1366 (m), 1325 (m), 1269 (s), 1220 (s), 1205 (s), 1 155 (s), 11 12 (m), 1081 (m), 1045 (m), 1030 (m), 962 (m), 941 (m), 893 (m), 835 (s), 806 (m), 744 (m), 715 (w), 690 (w), 657 (m), 628 (w), 596 (m), 557 (m), 531 (m). UV (MeOH): λ.sub.max (Ig ε)=286(4.26), 209 (4.21). MS (ESI): m/z (%)=197 [M+H].sup.+ (49), 219 [M+Na].sup.+ (100). HRMS (ESH+): m/z=219.06279 (0.1 ppm, ber.: 219.06278 [M+Na].sup.+).

Example 3

Producing 3-(2,4-Dimethoxyphenyl)-1-(2-hydroxy-4,6-dimethoxyphenyl)prop-2-en-1-one (8)

(5) Under an argon atmosphere, the acetophenone derivative (6) (4.80 g, 24.5 mmol, 1.0 eq.) and 2,4-Dimethoxybenzaldehyde (7) (6.01 g, 36.7 mmol, 1.5 eq.) were solubilised in ethanol (150 ml). A solution of NaOH (8.80 g, 220 mmol, 9.0 eq.) in distilled water (38 ml) was added dropwise. The reaction mixture was stirred for 17 hrs at room temperature. Subsequently, 1 M aqueous HCl solution (350 ml) was added and stirred for another 15 min. The solution was extracted three times with ethyl acetate (250 ml, respectively). The combined organic phases were dried over sodium sulphate, and the solvent removed in high vacuum. After column-chromatographic cleaning on silica gel [Petrol ether/Ethyl acetate (3: 1-1:1)] the chalcone (8) (5.87 g, 17.0 mmol, 70%) was obtained as yellow solid. DC [Petrol ether/Ethyl acetate (4:1)]: R.sub.f=0.32. Melting point.: 126-129° C. .sup.1H-NMR (400 MHz, CDCl.sub.3): d=14.54 (s, 1H, 2′-OH), 8.10 (d, J=15.7 Hz, 1H, ß-H), 7.90 (d, J=15.7 Hz, 1H, a-H), 7.54 (d, J=8.6 Hz, 1H, 6-H), 6.53 (dd, J=8.6, 2.4 Hz, 1H, 5-H), 6.47 (d, J=2.4 Hz, 1H, 3-H), 6.10 (d, J=2.4 Hz, 1H, 3′-H), 5.95 (d, J=2.4 Hz, 1H, 5′-H), 3.90 (s, 3H, 6′-OCH.sub.3), 3.89 (s, 3H, 2-OCH.sub.3), 3.85 (s, 3H, 4-OCH.sub.3), 3.83 (s, 3H, 4′-OCH.sub.3). .sup.13C-NMR (100 MHz, CDCl.sub.3): d=193.0 (C=0), 168.3 (C-6′), 165.8 (C-4′), 162.8 (C-4), 162.4 (C-2′), 160.2 (C-2), 138.3 (C-ß), 130.4 (C-6), 125.3 (C-a), 1 17.8 (C-1), 106.5 (C-1′), 105.5 (C-5), 98.4 (C-3), 93.8 (C-5′), 91.1 (C-3′), 55.7 (2′-OCH.sub.3), 55.5 (2-OCH.sub.3), 55.5 (4′-OCH.sub.3), 55.4 (4-OCH.sub.3), IR (Diamant-ATR): {tilde over (V)}=3120 (w, br.), 3082 (w, br.), 3000 (w), 2942 (m, br.), 2840 (w, br.), 1604 (s), 1547 (s), 1502 (s), 1451 (m), 1437 (m), 1414 (m), 1343 (m), 1315 (m), 1293 (m), 1268 (s), 1206 (s), 1158 (s), 1 106 (s), 1057(m), 1028 (s), 980 (m), 940 (m), 867 (m), 849 (m), 814 (s), 795 (s), 767 (m), 720 (m), 697 (m), 674 (m), 648 (m), 621 (m), 604 (m), 582 (m), 563 (m), UV (MeOH): λ.sub.max (Ig ε)=379 (4.52), 251 (3.95), 207 (4.60). MS (EI): m/z (%)=345 [M+H].sup.+ (47), 367 [M+Na].sup.+ (67), 71 1 [2M+Na].sup.+ (100). HRMS (ESI+): m/z=71 1.24176 (0.1 ppm, ber.: 71 1.24120 [2M+Na].sup.+).

Example 4

Producing 2-(2,4-Dimethoxyphenyl)-3-hydroxy-5,7-dimethoxy-4//-chromen-4-one (9)

(6) Under an argon atmosphere, the chalcone (8) (1.00 g, 2.90 mmol, 1.0 eq.) was solubilised in ethanol (40 ml). A solution of tert-Butylhydroperoxide (70% in H2O, 4.0 ml, 29.0 mmol, 10 eq.) and NaOH (1.74 g, 43.6 mmol, 15 eq.) in distilled H2O 2O (4 ml) was added and stirred for 23 hrs at room temperature. Subsequently, aqueous HCl solution (1.0 M, 100 ml) was added and extracted three times with ethyl acetate (80 ml, respectively). The combined organic phases were dried over sodium sulphate, and the solvent removed in high vacuum. After column-chromatographic cleaning on silica gel [Petrol ether/Ethyl acetate (1:4)] the flavonol (9) (395 mg, 1.10 mmol, 38%) was obtained as yellow solid, in addition to the aurone (10) (44 mg, 0.13 μmol, 4.5%). Likewise, the hydroxylated aurone derivative (11) was obtained (118 mg, 329 μmol, 11%). DC [Petrol ether/Ethyl acetate (1:4)]: R.sub.f=0.45. Melting point: 1 10-1 12° C. .sup.1H-NMR (600 MHz, CDCl.sub.3): d=7.50(d, J=8.4 Hz, 1H, 6′-CH), 6.78 (s, 1H, OH), 6.61 (dd, J=8.4, 2.4 Hz, 1H, 5′-CH), 6.58 (d, J=2.3 Hz, 1H, 3′-CH), 6.48 (d, J=2.3 Hz, 1H, 8-CH), 6.34 (d, J=2.3 Hz, 1H, 6-CH), 3.97 (s, 3H, 4′-OCH.sub.3), 3.87 (s, 6H, 2′-OCH3, 7-OCH.sub.3), 3.84 (s, 3H, 5-OCH)). .sup.13C-NMR (150 MHz, CDCl.sub.3): d=172.0 (C-4), 164.1 (C-7), 162.7 (C-4′), 160.6 (C-5), 159.6 (8C—C-10), 158.8 (C-2′), 142.7 (C-2), 138.6 (C-3), 131.9 (C-6′), 1 12.4 (C-1), 106.8 (4C—C-5C), 104.8 (C-5′), 99.2 (C-3′), 95.6 (C-6), 92.6 (C-8), 56.4 (4′-OCH.sub.3), 55.9 (5-OCH.sub.3), 55.8 (2′-OCH.sub.3), 55.5 (7-OCH.sub.3). IR (Diamant-ATR): {tilde over (V)}=3204 (m, br.), 3006 (w), 2961 (m), 2938 (m), 2840 (w), 1728 (m), 1658 (m), 1601 (s), 1499 (m), 1461 (m), 1435 (m), 1414 (m), 1373 (m), 1317 (m), 1299 (m), 1281 (m), 1252 (m), 1206 (s), 1 161 (s), 1 120 (m), 1092 (m), 1024 (m), 1002 (m), 967 (m), 936 (m), 918 (m), 873 (m), 814 (m), 742 (w), 677 (w), 639 (m), 599 (m), 552 (m). UV (MeOH): λ.sub.max (Ig ε)=338 (4.07), 286(3.89), 246 (4.32), 203 (4.64). MS (ESI): m/z (%)=359 [M+H].sup.+ (40), 381 [M+Na].sup.+ (56), 739 [2M+Na].sup.+ (100). HRMS (ESI+): m/z=739.20013 (0.02 ppm, ber.: 739.20028 [2M+Na].sup.+).

(7) By-product 2-(2,4-Dimethoxybenzyliden)-4,6-dimethoxybenzofuran-3(2/-/)-one (10): DC [Petrol ether/Ethyl acetate (1:4)]: =0.44. .sup.1H-NMR (400 MHz, CDCl.sub.3): δ=8.19 (d, J=8.7 Hz, 1H, 6′-H), 7.27 (s, 1H, 2C═CH), 6.58 (dd, J=8.7, 2.4 Hz, 1H, 5′-H), 6.45 (d, J=2.4 Hz, 1H, 3′-H), 6.36 (d, =1.9 Hz, 1H, 7H), 6.1 1 (d, J=1.9 Hz, 1H, 5H), 3.94 (s, 3H, 4-OCH.sub.3), 3.90 (s, 3H, 6-OCH.sub.3), 3.87 (s, 3H, 2′-OCH.sub.3), 3.86 (s, 3H, 4′OCH.sub.3). .sup.13C-NMR (100 MHz, CDCl.sub.3): d=180.6 (C-3), 168.6 (7-C—C-10), 168.4 (C-6), 162.2 (C-4′), 160.1 (C-2′), 159.3 (C-4), 146.8 (C-2), 132.8 (C-6′), 1 14.7 (C-1′), 105.7 (3C—C-4C), 105.5 (C-5′), 105.3 (2C═C), 98.0 (C-3′), 93.8 (C-5), 89.1 (C-7), 56.2 (4-OCH.sub.3), 56.0 (6-OCH.sub.3), 55.6 (2′—OCH.sub.3), 55.4 (4′-OCH.sub.3). IR (Diamant-ATR): {tilde over (V)}=2975 (w, br.), 2945 (w, br.), 2836 (w, br.), 1689 (m), 1648 (m), 1590 (s, br.), 1503 (m), 1447 (m), 1419 (m), 1362 (m), 1350 (m), 1321 (m), 1289 (m), 1243 (s), 1217 (s), 1201 (s), 1 155 (s), 1087 (s), 1033 (s), 946 (m), 917 (m), 890 (m), 815 (s), 788 (s), 720 (m), 695 (m), 674 (m), 633 (m), 589 (m), 548 (m). UV (MeOH): λ.sub.max (Ig ε)=403 (4.43), 252(3.93), 203 (4.53). MS (ESI): m/z (%)=343 [M+U].sup.+ (61), 365 [M+Na].sup.+ (100), 707 [2M+Na].sup.+ (97). HRMS (ESI+): m/z=365.09975 (0.5 ppm, ber.: 365.09956 [M+Na].sup.+).

(8) By-product (E)-2-((2,4-Dimethoxyphenyl)(hydroxy)methylen)-4,6-di methoxybenzofuran-3(2H)-one (11): DC [Petrol ether/Ethyl acetate (1:4)]: R.sub.f=0.63. Melting point: 177-180° C. .sup.1H-NMR (400 MHz, CDCl.sub.3): d=9.47 (s, OH), 7.19 (d, J=7.3 Hz, 6′-H), 6.57 (dd, J=7.3, 2.1 Hz, 5′-H), 6.56 (d, J=2.1 Hz, 3′-H), 6.53 (d, J=2.3 Hz, 7-H), 6.36 (d, J=2.3 Hz, 4-H), 3.99 (s, 3H, 3-COCH.sub.3), 3.86 (s, 3H, 5-COCH.sub.3), 3.83 (S, 3H, 4′-COCH.sub.3), 3.79 (s, 3H, 2′-COCH.sub.3). .sup.13C-NMR (100 MHz, CDCl.sub.3): d=170.72 (3-C), 162.87 (6-C), 161.80 (2-C), 160.85 (4′-C), 158.67 (2′-C), 157.01 (4-C), 155.80 (7-C—C-1-0), 132.46 (6′-C), 112.98 (C—OH), 104.70 (5′-C), 100.41 (1′-C), 99.15 (3′-C), 99.09 (3-C—C-4-C), 95.37 (5-C), 94.26 (7-C), 56.86 (4-C—CH.sub.3), 55.86 (6-C—CH.sub.3), 55.77 (2′-C—CH.sub.3), 55.68 (4′-C—CH.sub.3). IR (Diamant-ATR): {tilde over (V)}=3319 (m, br.), 3211 (w, 3004 (m), 2951 (m, br.), 2841 (m), 2678 (w, br.), 1703(m), 1603 (s), 1576 (s), 1510 (m), 1446 (m), 1368 (m), 1281 (m), 1256 (m), 1204 (5), 1155 (s), 1 110 (5), 1027 (a), 935 (m), 817 (m), 750 (m), 686 (m), 636 (m), 617 (m). UV (MeOH): λ.sub.max (Ig ε)=621 (1.71), 314 (3.71), 295 (3.72), 253 (3.86), 206 (4.39), 203 (4.39). MS (ESI): m/z (%)=381 [M+Na].sup.+ (100), 739 [2M+Na].sup.+ (42), HRMS (ESI+): m/z=381.09460 (1.10 ppm, ber.: 381.09502 [M+Na].sup.+).

Example 5

Producing 2-(2,4-Dihydroxyphenyl)-3,5,7-trihydroxy-4H-chromen-4-one (1, Morin)

(9) Under an argon atmosphere, the flavonol (9) (400 mg, 1.12 mmol, 1.0 eq.) was solubilised in acetic acid (99%, 10 ml) and HBr (48% in H.sub.2O, 50 ml) added. Subsequently, heating took place for 24 hrs under reflux. The solvent was removed from the raw material as much as possible and received in ethanol (2 ml). After adding petrol ether (100 ml), filtration and drying of the residue on the high vacuum, morin ((1), 220 mg, 728 μmol, 65%) was obtained as deep-red solid. RP-DC [Water/Methanol (1:1)]: Ri=0.35. Melting point: >250° C. .sup.1H-NMR (400 MHz, DMSO-d.sub.6): δ=12.64 (a, 5-C—OH, 1H), 10.72 (s, COH, 1H), 9.79 (s, 4′-COH, 1H), 9.35 (s, COH, 1H), 8.89 (s, COH, 1H), 7.24 (d, J=8.4 Hz, 6′-CH, 1H), 6.41 (d, J=2.1 Hz, 3′-CH, 1H), 6.36 (dd, J=8.5, 2.3 Hz, 5′-CH, 1H), 6.30 (d, J=2.1 Hz, 8-CH, 1H), 6.18 (d, J=2.0 Hz, 6-CH, 1H). .sup.13C-NMR (100 MHz, DMSO-d.sub.6): d=176.2 (C-4), 163.7 (C-7), 160.9 (C-5), 160.4 (C-4′), 156.8 (2C, C-2′, C-8a), 149.0 (C-2), 136.2 (C-3), 131.7 (C-6′), 109.3 (C-1′), 106.8 (C-5′), 103.6 (C-4a), 103.0 (C-2′), 98.0 (C-6), 93.4 (C-8). IR (Diamant-ATR): {tilde over (V)}=3212 (m, br.), 2731 (m, br.), 2341 (m, br.), 2116 (w, br.), 1995 (w, br.), 1920 (w, br.), 1655 (m), 1626 (m), 1594 (m), 1570 (m), 1515 (m), 1480 (m), 1412 (m), 1365 (m), 1311 (m), 1263 (m), 1224 (m), 1167 (s), 1102 (m), 1080 (m), 1011 (m), 983 (m), 969 (m), 874 (m), 833 (m), 805(m), 793 (m), 730 (m), 703 (m), 689 (m), 651 (m), 635 (m), 618 (m), 579 (m), 566 (m), 543 (m). UV (MeOH): λ.sub.max (Ig ε)=372 (4.12), 263 (4.25), 205 (4.59). MS (ESI): m/z (%)=301 [M−H]− (100), 303 [M+H]+(24), 325 [M+Na].sup.+ (100), 627 [2M+Na].sup.+ (23), 739 [2M+Na].sup.+ (100). HRMS (ESI+): m/z=325.03212 (0.92 ppm,bPer.: 325.03242 [M+Na].sup.+.