1. Synthesis of ( R)-Boc-2-methylproline via a Memory of Chirality Cyclization. Application to the Synthesis of Veliparib, a Poly(ADP-ribose) Polymerase Inhibitor
Lawrence Kolaczkowski, Jufang Barkalow, David M Barnes, Anthony Haight, Wayne Pritts, Adam Schellinger J Org Chem. 2019 Apr 19;84(8):4837-4845. doi: 10.1021/acs.joc.8b02866. Epub 2019 Feb 19.
( R)-Boc-2-methylproline (3a) was synthesized in good yield with excellent stereochemical control from alanine benzyl ester hydrochloride 11. The process, which is based on a modification of one described by Kawabata, proceeds in four steps and requires no chromatography. The product ( R)-Boc-2-methylproline (3a) was then carried forward in three steps to produce veliparib 1, a poly(ADP-ribose) polymerase inhibitor.
2. Synthesis of polyamide supports for use in peptide synthesis and as peptide-resin conjugates for antibody production
P Kanda, R C Kennedy, J T Sparrow Int J Pept Protein Res. 1991 Oct;38(4):385-91. doi: 10.1111/j.1399-3011.1991.tb01518.x.
We have synthesized beaded, hydrophilic cross-linked, aminoalkyl polydimethylacrylamide supports upon which peptides have been assembled using standard Boc or Fmoc chemistry in automated equipment. The resins were prepared by the free radical-initiated co-polymerization of N,N-dimethylacrylamide, N,N'-bisacrylyl-1,3-diaminopropane, and a functional monomer which were contained in a reverse-phase, detergent-emulsified suspension. The functional monomers used were N-(2-(methylsulfonyl)ethyloxycarbonyl)-allyl-amine (MSC-allylamine), N-acrylyl-1,6-diaminohexane hydrochloride or N-methacrylyl-1,3-diamino-propane hydrochloride. The MSC protecting group was removed by treatment of the resin with methanolic base during workup. After coupling of N-alpha-t-butyloxycarbonyl-alanine (Boc-alanine), amino acid analyses gave resin loading capacities between 0.15 mmol/g and 1.4 mmol/g, depending on the concentration and composition of the functional monomer. The resulting polymers were highly swollen by polar solvents including aqueous buffers. Peptides were synthesized on these supports after attaching the first amino acid directly or through a cleavable ester linker. When the carboxyl-terminal amino acid was coupled as the 4-oxymethylbenzoic acid derivative, the peptide could be deprotected and remain attached to the hydrophilic polymer since the peptide-benzyl ester bond was stable to HF deprotection at 0 degrees in the presence of 10% anisole and 1% ethanedithiol. The resulting peptidyl-resin could be swollen in aqueous buffers and injected into animals for the production of antibodies.
3. An efficient enantioselective synthesis of ( S)-α-methyl-serine methyl ester hydrochloride via asymmetrically catalyzed amination
Qiong Xiao, Yi-Fan Tang, Ping Xie J Asian Nat Prod Res. 2020 Jan;22(1):61-68. doi: 10.1080/10286020.2019.1634058. Epub 2019 Jul 16.
We present the synthesis of enantiomerically pure (S)-α-methyl-serine methyl ester hydrochloride from 2-methyl-3-((4-(trifluoromethyl)benzyl)oxy)propanal and di-p-chlorobenzyl azodicarboxylate via asymmetrically catalyzed amination with naphthylalanine derivative catalyst. The application of the organocatalyst of D-3-(1-Naphthyl)-alanine is the key step in the synthesis and ensures the product is obtained with high levels of stereocontrol.