Synthesis strategy for gap protecting group

Abstract

The present invention relates to a novel synthesis method to form particular molecules. These molecules have multiple uses, most notably in the field of protecting groups used throughout organic and synthetic chemistry. The disclosed method is safer, more cost- and time-effective, and more amenable to large scale production than those currently known in the art. The protecting groups synthesized are useful in GAP peptide synthesis.

Claims

1. A protecting group for chemical synthesis, selected from the group consisting of: ##STR00014## wherein: in (1E): Y is selected from the group consisting of: —S— and —NH—; R′ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and R″ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3- ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and in (1F): Y is selected from the group consisting of: —O—, —S—, and —NH—; Z is selected from the group consisting of: —O—, —S—, —NMe, and —NH—; R′ is selected from the group consisting of: -Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and R″ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20.

2. A method comprising the step of synthesizing a protecting group, wherein the protecting group is selected from a group consisting of: ##STR00015## wherein: in (1B): R is selected from the group consisting of: —H, -Me, and —OMe; Y is selected from the group consisting of: —S— and —NH—; R′ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and R″ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; in (1E): Y is selected from the group consisting of: —S— and —NH—; R′ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and R″ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and in (1C) and (1F): R is selected from the group consisting of: —H, -Me, and —OMe; Y is selected from the group consisting of: —O—, —S—, and —NH—; Z is selected from the group consisting of: —O—, —S—, —NMe, and —NH—; R′ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and R″ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20.

3. The method of claim 2, wherein protecting group: ##STR00016## is produced by the following: ##STR00017## wherein: PG stands for protecting group; R is selected from the group consisting of: —H, -Me, and —OMe; Y is selected from the group consisting of: —S— and —NH—; X is selected from the group consisting of: —Br, —CI, —I, -OTs, -OMs, and -OTf; R′ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and R″ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20.

4. The method of claim 2, wherein the protecting group (1C) is synthesized by the following reaction: ##STR00018## where: PG stands for protecting group; TMS is trimethylsilyl; MOM is methoxymethyl; BOM is benzyloxymethyl; TBS is tert-butyldimethylsilyl; TIPS is triisopropylsilyl; and TBDPS is tert-butyldiphenylsilyl.

5. The method of claim 2, wherein protecting group: ##STR00019## is produced by the following: ##STR00020## wherein: PG stands for protecting group; Y is selected from the group consisting of: —S— and —NH—; X is selected from the group consisting of: —Br, —Cl, —I, -OTs, -OMs, and -OTf; R′ is selected from the group consisting of Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and R″ is selected from the group consisting of Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20.

6. The method of claim 2, wherein the protecting group (1F) is synthesized by the following reaction: ##STR00021## where: P(stands tor protecting group; TMS is trimethylsilyl; MOM is methoxymethyl; BOM is benzyloxymethyl; TBS is tert-butyldimethylsilyl; TIPS is triisopropylsilyl; and TBDPS is tert-butyldiphenylsilyl.

7. A method of performing Group Assisted Purification (GAP) peptide synthesis, wherein the method comprises the steps of attaching a protecting group to an amino acid via a nucleophilic moiety followed by Fmoc-tBu-based solution phase peptide synthesis (SoIPPS) coupling reactions on the resulting amino acid having the attached protecting group; wherein the protecting group comprises at least one of: ##STR00022## wherein: in (1B): R is selected from the group consisting of: —H, -Me, and —OMe; Y is selected from the group consisting of: —S— and —NH—; R′ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and R″ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; in (1E): Y is selected from the group consisting of: —S—, and —NH—; R′ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and R″ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and in (1C) and (1F): R is selected from the group consisting of: —H, -Me, and —OMe; Y is selected from the group consisting of: —O—, —S—, and —NH—; Z is selected from the group consisting of: —O—, —S—, —NMe, and —NH—; R′ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20; and R″ is selected from the group consisting of: Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, and —(CH2)n-CH3 where n=any integer >0 and <20.

8. The method of claim 7, wherein the reactions occur in ethyl acetate.

9. The method of claim 7, wherein the reactions occur in dichloromethane.

10. The method of claim 7, wherein the reactions occur in dimethylformamide.

11. The method of claim 7, wherein the reactions occur in 2-methyltetrahydrofuran.

12. The method of claim 7, wherein the reactions occur in propylene carbonate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing and other objects, features, and advantages of the disclosure will be apparent from the following description of embodiments as illustrated in the accompanying drawings, in which reference characters refer to the same parts throughout the various views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating principles of the disclosure. The figures are used as non-limiting examples, only intended to portray preferred embodiments without limiting the scope of this disclosure:

(2) FIG. 1 depicts a step in a non-limiting embodiment of the present invention, in which 4-bromobenzylalcohol is exemplarily protected with a TMS group.

(3) FIG. 2 depicts a step in a non-limiting embodiment of the present invention, in which TMS-protected 4-bromobenzylalcohol is transformed into a Grignard reagent and subsequently converted to TMS-protected HOBnDpp.

(4) FIG. 3 depicts a step in a non-limiting embodiment of the present invention, in TMS-protected HOBnDpp is TMS-deprotected.

(5) FIG. 4 depicts a step in a non-limiting embodiment of the present invention, in which TMS-protected 4-bromobenzylalcohol is converted to TMS-protected HOBnDpp using a butyllithium reagent.

(6) FIG. 5 depicts non-limiting, representative protecting groups that can be synthesized using the present invention. The nucleophilic moiety of each depicted protecting group is labelled.

(7) FIG. 6 depicts a schematic by which multiple protecting groups, including some of those of FIG. 5, can be synthesized.

(8) FIG. 7 depicts a schematic by which multiple protecting groups, including some of those of FIG. 5, can be synthesized.

(9) FIG. 8 depicts, as a non-limiting example, a schematic for synthesizing aniline diphenylphosphine oxide from halogenated nitrobenzene.

(10) FIG. 9 depicts a schematic by which multiple protecting groups, including some of those of FIG. 5, can be synthesized.

(11) FIG. 10 depicts a schematic by which multiple protecting groups, including some of those of FIG. 5, can be synthesized.

(12) FIG. 11 depicts, as a non-limiting example, the attachment of a protecting group from FIG. 5 to a general amino acid to protect the C-terminus of the amino acid.

DETAILED DESCRIPTION OF THE DISCLOSURE

(13) In the Summary of the Invention above and in the Detailed Description of the Invention, and the claims below, and in the accompanying drawings, reference is made to particular features of the invention. It is to be understood that the disclosure of the invention in this specification includes all possible combinations of such particular features. For example, where a particular feature is disclosed in the context of a particular aspect or embodiment of the invention, or a particular claim, that feature can also be used, to the extent possible, in combination with and/or in the context of other particular aspects and embodiments of the invention, and in the invention generally.

(14) All of the compositions and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions and/or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit, and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope, and concept of the invention as defined by the appended claims.

(15) The term “comprises” and grammatical equivalents thereof are used herein to mean that other components, ingredients, steps, etc. are optionally present. For example, an article “comprising” (or “which comprises”) components A, B, and C can consist of (i.e., contain only) components A, B, and C, or can contain not only components A, B, and C but also one or more other components.

(16) Where reference if made herein to a method comprising two or more defined steps, the defined steps can be carried out in any order or simultaneously (except where the context excludes that possibility), and the method can include one or more other steps which are carried out before any of the defined steps, between two of the defined steps, or after all the defined steps (except where the context excludes that possibility).

(17) The term “at least” followed by a number is used herein to denote the start of a range beginning with that number (which may be a range having an upper limit or no upper limit, depending on the variable being defined). For example, “at least 1” means 1 or more than 1. The term “at most” followed by a number is used herein to denote the end of a range ending with that number (which may be a range having 1 or 0 as its lower limit, or a range having no lower limit, depending upon the variable being defined). For example, “at most 4” means 4 or less than 4, and “at most 40%” means 40% or less than 40%. When, in this specification, a range is given as “(a first number) to (a second number)” or “(a first number)-(a second number),” this means a range whose lower limit is the first number and whose upper limit is the second number. For example, 25 to 100 mm means a range whose lower limit is 25 mm, and whose upper limit is 100 mm.

(18) The term “first” is used to distinguish one element from another element and is not meant denote that an element is the primary or initial element in any given sequence of elements. For example, “a first amino acid” does not signify that the amino acid is the first in a sequence of amino acids or the first amino acid to be reacted. Instead, “a first amino acid” only indicates that the amino acid is separate and distinguishable from another amino acid, such as “a second amino acid.”

(19) The term “coupling reaction” is used to refer generally to the formation of a bond between two constituent molecules facilitated by a “coupling reagent.” In peptide chemistry, these coupling reactions can occur via many different mechanisms under many different reaction conditions that can completely depend on the coupling reagent used. For example, a coupling reagent can “activate” the carboxylic acid of a constituent molecule such that the carbonyl carbon can be more prone to nucleophilic attack. Coupling reactions can result in the loss of a water molecule during the formation of the bond between the two constituent molecules (see Chandrudu 2013, Mollica 2013, Shelton 2013, Amblard 2006, Bachem 2016).

(20) In many types of protecting schemes for peptide synthesis, a repetition of similar reactions occurs to grow the peptide chain. Generally, either the N- or C-terminus of each amino acid added to the chain is initially protected, and the other terminus of the amino acid is free to participate in a coupling reaction. After addition to the chain via the initially-free terminus, a deprotection reaction is run, freeing up the protected N- or C-terminus to participate in a subsequent coupling reaction to create a peptide bond with the next amino acid. For example, in Fmoc/tBu-based peptide synthesis, the Fmoc group protects the N-terminus of amino acids, and side chains of amino acids are protected with tBu-based protecting groups, including but not limited to butyl, trityl (triphenylmethyl), Boc (butyloxycarbonyl), Pbf (2,2,4,6,7-pentamethyl-2,3-dihydrobenzofuran-S-sulfonyl), Pmc (2,2,5,7,8-pentamethylchromane-6-sulfonyl), and Acm (acetamidomethyl) (some amino acids do not require side-chain protection because the side-chains are naturally inert to coupling and deprotection conditions). The C-terminus of the primary amino acid in the peptide sequence is connected to and protected by a resin or polymer in SPPS, and a protecting group in SolPPS. The Fmoc/tBu peptide synthesis scheme is designed such that the Fmoc group on the N-termini of amino acids is base-labile, and treatment with the proper deprotection base removes the Fmoc group from the N-termini without interfering with any C-terminus connections or side-chain protections. Once the deprotection reaction is performed, the N-terminus of the primary amino acid is free, while the C-terminus and side chain are protected or otherwise inert. Then, the next amino acid, with the N-terminus Fmoc-protected and the side chain protected or naturally inert, is activated at the free C-terminus with a coupling reagent, and such activation facilitates nucleophilic attack by the free N-terminus of the primary amino acid on the activated carbonyl to form a peptide bond between the primary and next amino acid. This process is repeated until the proper peptide sequence is achieved. After Fmoc deprotection of the final amino acid, the peptide is still protected at the C-terminus and at the side chains. A global deprotection with a strong acid cocktail such as a TFA-based cocktail is then performed to remove all of the side-chain protecting groups; in some cases, the C-terminal resin or protecting group can also be cleaved.

(21) Commonly used abbreviations for different chemical entities and functional groups may be used throughout. “PG” may be used to stand for “protecting group;” “TMS” for “trimethylsilyl;” “MOM” for “methoxymethyl;” “BOM” for “benzyloxymethyl;” “TBS” for “tert-butyldimethylsilyl;” “TIPS” for “triisopropylsilyl;” “TBDPS” for “tert-butyldiphenylsilyl;” “Me” for “methyl;” “tBu” for “tert-butyl;” “alkyl” for “—(CH.sub.2).sub.n—CH.sub.3 where n=any integer >0 or <20;” “OMe” for “methoxy;” “Ph” for “phenyl;” “2-ClPh” for “2-chlorophenyl;” “4-ClPh” for “4-chlorophenyl;” “3-ClPh” for “3-chlorophenyl;” “3,5-Cl.sub.2Ph” for “3,5-dichlorophenyl;” “OTs” for “4-methylbenzenesulfonate;” “OMs” for “methansulfonate;” “OTf” for “trifluoromethanesulfonate.”

(22) It is therefore an embodiment of the present disclosure to provide an improved synthesis strategy for the creation of GAP protecting groups used in multiple iterations of GAP peptide synthesis. In designing this method, it was apparent that the method should seek to be as economical, safe, and scalable as possible while maintaining benefits of known synthesis strategies, namely facile purification and isolation through precipitation as opposed to column chromatography or recrystallization. The method would need to be designed to address some specific issues, including shortening the time of synthesis, avoiding undesirable byproducts, replacing undesirable reagents, and adapting the reaction conditions to be more amenable to a large-scale synthesis.

(23) In one embodiment, the present invention provides a method of synthesizing a protecting group, wherein the protecting group is selected from a group consisting of:

(24) ##STR00001##
wherein: R is selected from the group consisting of: H, Me, and OMe; Y is selected from the group consisting of: O, S, and NH; Z is selected from the group consisting of: O, S, NMe, and NH; R′ is selected from the group consisting of: H, Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, —(CH2)n-CH3 where n=any integer >0 or <20; and R″ is selected from the group consisting of: H, Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, —(CH2)n-CH3 where n=any integer >0 or <20.

(25) In another embodiment, the present invention provides a method of forming a protecting group:

(26) ##STR00002##
which is produced by the following:

(27) ##STR00003##
wherein, said protecting group is formed by stirring trimethylsilyl chloride (TMSCl) and DIPEA with 4-bromobenzylalcohol at 0° C.; isolating the TMS-protected bromobenzylalcohol; refluxing the TMS-protected product with magnesium in tetrahydrofuran; slowly adding diphenylchlorophosphine to the reaction at 0° C.; stirring the resulting phosphine moiety with hydrogen peroxide; and removing the TMS group with 2M HCl (aq).

(28) In another embodiment, the present invention discloses a method of synthesizing a protecting group:

(29) ##STR00004##
which is produced by the following:

(30) ##STR00005## R=H, Me, OMe Y=O, S, NH X=Br, Cl, I, OTs, OMs, OTf R′=H, Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, —(CH2)n-CH3 where n=any integer >0 or <20 R″=H, Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, —(CH2)n-CH3 where n=any integer >0 or <20.
wherein said protecting group is produced by reacting a halogenated, protected benzyl alcohol, primary amine, secondary amine, or sulfur moiety (XBnYPG) with either magnesium (to form the Grignard reagent with THF reflux) or nBuLi (at −80° C.); slowly adding diphenylchlorophosphine (at 0° C. for the Grignard reagent or at −80° C. for the butyllithium reagent); stirring the resulting phosphine moiety with hydrogen peroxide; and deprotecting the resulting phosphine oxide with HCl at room temperature or by boiling as necessary.

(31) In another embodiment, the present invention discloses a method of forming protecting group:

(32) ##STR00006##
which is produced by the following:

(33) ##STR00007## R=H, Me, OMe Y=O, S, NH Z=O, S, NMe, NH R′=H, Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, —(CH2)n-CH3 where n=any integer >0 or <20 R″=H, Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, —(CH2)n-CH3 where n=any integer >0 or <20.
wherein a phenyl ring with a protected alcohol, sulfur, or amine moiety, and a free alcohol, sulfur, or amine moiety (HZBnYPG), is reacted with diphenylchlorophosphine; the resulting phosphine is oxidized with hydrogen peroxide; and the protecting group is removed with 2M HCl (room temperature or boiling as necessary).

(34) In another embodiment, the present invention discloses a method of forming protecting group:

(35) ##STR00008##
which is produced by the following:

(36) ##STR00009## R=H, Me, OMe X=Br, Cl, I, OTs, OMs, OTf
wherein halogenated nitrobenzene is reacted with magnesium (at reflux to yield Grignard reagent) or nBuLi at −80° C.; diphenylchlorophosphine is slowly added (at 0° C. for Grignard reagent or −80° C. for butyllithium reagent); the resulting phosphine product is oxidized with hydrogen peroxide; and the nitro group is subsequently reduced to a primary amine with a reducing agent such as sodium borohydride or hydrogen gas with transition metal catalysts.

(37) In another embodiment, the present invention discloses a method of forming protecting group:

(38) ##STR00010##
which is produced by the following:

(39) ##STR00011## Y=O, S, NH X=Br, Cl, I, OTs, OMs, OTf R′=H, Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, —(CH2)n-CH3 where n=any integer >0 or <20 R″=H, Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, —(CH2)n-CH3 where n=any integer >0 or <20
wherein said protecting group is produced by reacting a protected benzyl alcohol, primary amine, secondary amine, or sulfur moiety (XBnYPG) that is halogenated at any available para, ortho, or meta position with either magnesium (to form the Grignard reagent with THF reflux) or nBuLi (at −80° C.); slowly adding diphenylchlorophosphine (at 0° C. for the Grignard reagent or at −80° C. for the butyllithium reagent); stirring the resulting phosphine moiety with hydrogen peroxide; and deprotecting the resulting phosphine oxide with HCl at room temperature or by boiling as necessary. In this particular embodiment, the resulting diphenylphosphine oxide can be attached in any of the available para, ortho, or meta positions on the benzene ring.

(40) In another embodiment, the present invention discloses a method of forming protecting group:

(41) ##STR00012##
which is produced by the following:

(42) ##STR00013## R=H, Me, and OMe; Y=O, S, and NH; and Z=O, S, NMe, and NH. R′=H, Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, —(CH2)n-CH3 where n=any integer >0 or <20 R″=H, Me, iPr, tBu, Ph, 2-ClPh, 4-ClPh, 3-ClPh, 3,5-Cl2Ph, —(CH2)n-CH3 where n=any integer >0 or <20.
wherein a phenyl ring with a protected alcohol, sulfur, or amine moiety, and a free alcohol, sulfur, or amine moiety (HZBnYPG), is reacted with diphenylchlorophosphine; the resulting phosphine is oxidized with hydrogen peroxide; and the protecting group is removed with 2M HCl (room temperature or boiling as necessary). In this non-limiting embodiment, the diphenylphosphine oxide can be attached to the phenyl ring via the previously free alcohol, sulfur, or amine moiety in any of the available para, ortho, or meta positions.

(43) In another embodiment, the present invention discloses a method of performing Group Assisted Purification (GAP) peptide synthesis, wherein the method comprises the steps of attaching protecting group 1E or 1F to an amino acid via the nucleophilic moiety followed by Fmoc-tBu-based solution phase peptide synthesis (SolPPS) coupling reactions on the resulting amino acid having the attached protecting group. Such method of GAP-PS may further include the reaction occurring in ethyl acetate, dichloromethane, or dimethylformamide.

(44) The principles discussed herein may be embodied in many different forms. The preferred embodiments of the present disclosure will now be described where for completeness, reference should be made at least to the Figures.

(45) FIG. 5 depicts representative protecting groups that can be synthesized using the present invention. In all of the above embodiments, and as a non-limiting example, the final step in the synthesis yields a nucleophilic alcohol, sulfur, or amine moiety 6, 7, 8, 9, 10, 11 (FIG. 5) on the protecting group that can be reacted with a constituent of a molecule of interest to effectuate “protection” of that particular constituent. In a non-limiting example, the nucleophilic moiety from a protecting group shown in FIG. 5 can be reacted with an activated C-terminus of an amino acid to yield a C-terminus protected amino acid (FIG. 11). GAP peptides synthesis can then proceed in the C to N direction.

(46) FIGS. 6-7 depict other non-limiting embodiments of the present invention to yield protecting groups of different makeup and uses.

(47) FIG. 8 depicts a schematic for synthesizing the protecting group aniline diphenylphosphine oxide, or NH.sub.2PhDpp.

(48) FIG. 9 depicts a non-limiting example of the synthesis of a protecting group, wherein the diphenylphosphine oxide moiety is optionally in the para, ortho, or meta position relative to the nucleophilic moiety.

(49) FIG. 10 depicts a non-limiting example of the synthesis of a protecting group, wherein the diphenylphosphine oxide moiety (attached via an alcohol, sulfur, amine, or amino methyl group) is optionally in the para, ortho, or meta position relative to the nucleophilic moiety.

Example 1

(50) For a first application of a new protecting group synthesis method, and as a non-limiting example of the present invention, the GAP protecting group HOBnDpp was formed.

(51) Synthesis of TMS-protected 4-bromobenzylalcohol 1. 39 g of 1 (FIG. 1) was first dissolved in 500 mL diethyl ether in a 1 L round-bottomed flask and cooled down to 0° C. in an ice bath. 36 mL of DIPEA was added to the solution, followed by a dropwise addition of 27 mL TMS chloride, and the reaction was stirred for about thirty minutes. DIPEA hydrochloride precipitated as a white solid and was filtered out, leaving 2 dissolved in diethyl ether. This solution was concentrated down to an oil and subjected directly to the next reaction.

(52) Synthesis of Grignard reagent 3.2 from the previous reaction was dissolved in 300 mL of dry, distilled THF. 3.8 g of magnesium shavings were added to the solution and the reaction was stirred at reflux for about three hours, or until all of the magnesium dissolved, to obtain 3 (FIG. 2). This product remained preserved in THF solution under nitrogen atmosphere and was directly subjected to the next reaction.

(53) Synthesis of protected TMSOBnDpp 4.3 from the previous reaction dissolved in THF was cooled down to 0° C., and 15 mL of diphenylchlorophosphine was slowly added and stirred for about thirty minutes. 100 mL of H.sub.2O was added to quench the reaction and subsequently extracted, and 30 mL of 30% hydrogen peroxide was added and stirred with the solution for about fifteen minutes to yield 4 in the THF layer (FIG. 2). The water layer was extracted, and the THF layer with 4 was directly subjected to the next reaction.

(54) Lithium-halogen exchange in lieu of Grignard reagent. 2 (FIG. 1) was dissolved in 250 mL of dry, distilled THF, and the solution was cooled down to −80° C. in a dry ice/acetone bath. 100 mL of 1.6M nBuLi solution in hexanes was added dropwise under a nitrogen atmosphere, followed by a dropwise addition of diphenylchlorophosphine. That was allowed to stir for about thirty minutes, and after addition of 100 mL water, 30 mL of 30% hydrogen peroxide was added and stirred with the reaction mixture for about fifteen minutes to yield 4 (FIG. 4).

(55) Synthesis of HOBnDpp 5. 300 mL of 2M HCl (aq) was added to 4 dissolved in THF from the previous reaction and stirred overnight. The HCl layer was then extracted, and the THF layer was dried and then concentrated to dryness to yield 5 at about 95% purity (FIG. 3).

(56) General methods: All solvents were ACS grade and used without additional purification. LCMS analysis was conducted using a Thermo TSQ Quantum Access Mass Spectrometer equipped with a PAL autosampler and Agilent solvent pump.

(57) Those skilled in the art will recognize that the methods and systems of the present disclosure may be implemented in many manners and as such are not to be limited by the foregoing exemplary embodiments and examples. In other words, functional elements being performed by single or multiple components, in various combinations of hardware and software or firmware, and individual functions, may be distributed among various software applications at either the client level or server level or both. In this regard, any number of the features of the different embodiments described herein may be combined into single or multiple embodiments, and alternate embodiments having fewer than, or more than, all of the features described herein are possible.

(58) Functionality may also be, in whole or in part, distributed among multiple components, in manners now known or to become known. Thus, myriad combinations are possible in achieving the functions, features, and preferences described herein. Moreover, the scope of the present disclosure covers conventionally known manners for carrying out the described features as well as those variations and modifications that may be made to the processes, composition, or compounds described herein as would be understood by those skilled in the art now and hereafter.

(59) Furthermore, the embodiments of methods presented and described as diagrams, schematics or flowcharts in this disclosure (such as the Figures) are provided by way of example in order to provide a more complete understanding of the technology. The disclosed methods are not limited to the operations and logical flow presented herein. Alternative embodiments are contemplated in which the order of the various operations is altered and in which sub-operations described as being part of a larger operation are performed independently. While various embodiments have been described for purposes of this disclosure, such embodiments should not be deemed to limit the teaching of this disclosure to those embodiments. Various changes and modifications may be made to the elements and operations described above to obtain a result that remains within the scope of the systems and processes described in this disclosure.

RELATED REFERENCES

(60) The below references are incorporated herein by reference as examples. An, G.; Seifert, C.; Li, G. N-Phosphonyl/phosphinyl imines and group-assisted purification (GAP) chemistry/technology. Org. Biomol. Chem. 2015, 13, 1600-1617. Ai, T.; Li, G. Chiral N-phosphonyl imine chemistry: Asymmetric synthesis of αβ-diamino esters by reacting phosphonyl imines with glycine enolates. Bioorg. Med. Chem. Lett. 2009, 19, 3967-3969. Han, J.; Ai, T.; Nguyen, T.; Li, G. Chiral N-phosphonyl imine chemistry: asymmetric additions of ester enolates for the synthesis of β-amino acids. Chem. Biol. Drug Des. 2008, 72, 120-126. Kattamuri, P. V.; Ai, T.; Pindi, S.; Sun, Y.; Gu, P.; Shi, M.; Li, G. Asymmetric Synthesis of α-Amino-1,3-dithianes via Chiral N-Phosphonyl Imine-Based Umpolung Reaction Without Using Chromatography and Recrystallization. J. Org. Chem. 2011, 76, 2792-2797. Kattuboina, A.; Kaur, P.; Nguyen, T.; Li, G. Chiral N-phosphonyl imine chemistry: asymmetric 1,2-additions of allylmagnesium bromides. Tetrahedron Lett. 2008, 49, 3722-3724. Kattuboina, A.; Li, G. Chiral N-phosphonyl imine chemistry: new reagents and their applications for asymmetric reactions. Tetrahedron Lett. 2008, 49, 1573-1577. Kaur, P.; Wever, W.; Pindi, S.; Milles, R.; Gu, P.; Shi, M.; Li, G. The GAP chemistry for chiral N-phosphonyl imine-based Strecker reaction. Green Chem. 2011, 13, 1288-1292. Pindi, S.; Kaur, P.; Shakya, G.; Li, G. N-Phosphinyl Imine Chemistry (I): Design and Synthesis of Novel N-Phosphinyl Imines and their Application to Asymmetric aza-Henry Reaction. Chem. Biol. Drug. Des. 2011, 77, 20-29. Xie, J.-b.; Luo, J.; Winn, T. R.; Cordes, D. B.; Li, G. Group-assisted purification (GAP) chemistry for the synthesis of Velcade via asymmetric borylation of Nphosphinylimines. Beilstein J. Org. Chem. 2014, 10, 746-751. Dailler, D.; Danoun, G.; Baudoin, O. A General and Scalable Synthesis of Aeruginosin Marine Natural Products Based on Two Strategic C(sp(3))-H Activation Reactions. Angewandte Chemie-International Edition 2015, 54, 4919-4922. Kaufmann, E.; Hattori, H.; Miyatake-Ondozabal, H.; Gademann, K. Total Synthesis of the Glycosylated Macrolide Antibiotic Fidaxomicin. Organic Letters 2015, 17, 3514-3517. Sharma, P. K.; Romanczyk, L. J.; Kondaveti, L.; Reddy, B.; Arumugasamy, J.; Lombardy, R.; Gou, Y.; Schroeter, H. Total Synthesis of Proanthocyanidin A1, A2, and Their Stereoisomers. Organic Letters 2015, 17, 2306-2309. Wuts, P. G. M. Greene's Protective Groups in Organic Synthesis. 5 ed.; John Wiley & Sons, Inc: New Jersey, 2014. Isidro-Llobet, A.; Alvarez, M.; Albericio, F. Amino Acid-Protecting Groups. Chem. Rev. 2009, 109, 2455-2504. Behrendt, R.; Huber, S.; Marti, R.; White, P. New t-butyl based aspartate protecting groups preventing aspartimide formation in Fmoc SPPS. Journal of Peptide Science 2015, 21, 680-687. Chandrudu, S.; Simerska, P.; Toth, I. Chemical Methods for Peptide and Protein Production. Molecules 2013, 18, 4373. Mochizuki, M.; Tsuda, S.; Tanimura, K.; Nishiuchi, Y. Regioselective Formation of Multiple Disulfide Bonds with the Aid of Postsynthetic S-Tritylation. Organic Letters 2015, 17, 2202-2205. Merrifield, R. B. Solid Phase Peptide Synthesis. I. The Synthesis of a Tetrapeptide. J. Am. Chem. Soc. 1963, 85, 2149. Mollica, A.; Pinnen, F.; Azzurra, S.; Costante, R. The Evolution of Peptide Synthesis: From Early Days to Small Molecular Machines. Curr. Bioact. Compd. 2013, 9, 184-202. Shelton, P. T.; Jensen, K. J. Linkers, Resins, and General Procedures for Solid-Phase Peptide Synthesis. In Peptide Synthesis and Applications, 2nd Edition, Jensen, K. J.; Shelton, P. T.; Pedersen, S. L., Eds. Humana Press Inc: Totowa, 2013; Vol. 1047, pp 23-41. An, G.; Seifert, C.; Sun, H.; Pan, Y.; Li, G. Group-Assisted Purification (GAP) for Protection of Amino Acids Using N-Phosphonyl Functional Groups. Heterocycles 2015, 90, 344-356. An, G.; Zhou, W.; Xu, X.; Pan, Y.; Li, G. Solution-Phase-Peptide Synthesis Without Purification of Column Chromatography and Recrystallization by Protecting Amino Acid Esters with Phosphinyl Chloride. Heterocycles 2015, 90, 1405-1418. Wu, J.; An, G.; Lin, S.; Xie, J.; Zhou, W.; Sun, H.; Pan, Y.; Li, G. Solution phase peptide synthesis via the group-assisted purification (GAP) chemistry without using chromatography and recrystallization. Chem. Commun. 2014, 50, 1259-1261. Brieke, C.; Cryle, M. J. A Facile Fmoc Solid Phase Synthesis Strategy To Access Epimerization-Prone Biosynthetic Intermediates of Glycopeptide Antibiotics. Organic Letters 2014, 16, 2454-2457. Chen, C.-C.; Rajagopal, B.; Liu, X. Y.; Chen, K. L.; Tyan, Y.-C.; Lin, F.; Lin, P.-C. A mild removal of Fmoc group using sodium azide. Amino Acids 2014, 46, 367-374. Spinella, M.; De Marco, R.; Belsito, E. L.; Leggio, A.; Liguori, A. The dimethylsulfoxonium methylide as unique reagent for the simultaneous deprotection of amino and carboxyl function of N-Fmoc-α-amino acid and N-Fmoc-peptide esters. Tetrahedron 2013, 69, 2010-2016. Amblard, M.; Enomoto, H.; Subra, G.; Fehrentz, J.-A.; Martinez, J. The Fundamentals of Fmoc Solid-Phase Peptide Synthesis. Idenshi Igaku Mook 2012, 21, 36-42. Shi, M.; Yang, Y.; Zhou, X.; Cai, L.; Fang, C.; Wang, C.; Sun, H.; Sun, Y.; Gao, Y.; Gu, J.; Fawcett, J. P. Determination of thymopentin in beagle dog blood by liquid chromatography with tandem mass spectrometry and its application to a preclinical pharmacokinetic study. Journal of Separation Science 2015, 38, 1351-1357. Zhu, M.-X.; Wan, W.-L.; Li, H.-S.; Wang, J.; Chen, G.-A.; Ke, X.-Y. Thymopentin enhances the generation of T-cell lineage derived from human embryonic stem cells in vitro. Experimental Cell Research 2015, 331, 387-398. Fu, T. T.; Qiao, H. W.; Peng, Z. M.; Hu, G. B.; Wu, X. J.; Gao, Y. X.; Zhao, Y. F. Palladium-catalyzed air-based oxidative coupling of arylboronic acids with H-phosphine oxides leading to aryl phosphine oxides. Organic & Biomolecular Chemistry 2014, 12, 2895-2902. Lawrenson, S. B.; Arav, R.; North, M. The greening of peptide synthesis. Green Chemistry 2017, 19, 1685. Isidro-Llobet, A.; Alvarez, M.; Albericio, F. Amino Acid-Protecting Groups. Chemical Reviews 2009, 109, 2455-2504. Jensen, Knud J. Chapter 1: Peptide Synthesis. Pharmaceutical Formulation Development of Peptides and Proteins 2013, pages 1-16. Amblard, M.; Fehrentz, J. A.; Martinez, J.; Subra, G. Methods and Protocols of Modern Solid Phase Peptide Synthesis. Molecular Biotechnology 2006, 33, 239-254. Bachem. Tips and Trick for Solid Phase Peptide Synthesis from the Experts at Bachem. Solid Phase Peptide Synthesis 2016, pages 1-55. P. Wuts and T. Greene, Greene's Protective Groups in Organic Synthesis 4th ed. John Wiley & Sons, 2006.