Novel thiol- and thioether-containing amino acids: cystathionine and homocysteine families

Abstract 

Natural L-homocysteine and L,L-cystathionine, along with a series of unnatural analogues, have been prepared from L-aspartic and L-glutamic acid. Manipulation of the protected derivatives provided x-iodoamino acids, which were used in thioalkylation reactions of sulfur nucleophiles, such as the ester of L-cysteine and potassium thioacetate.

A practical route to β2,3-amino acids with alkyl side chains

Longobardo et al. SpringerPlus (2015) 4:553DOI 10.1186/s40064-015-1351-6
RESEARCH
A practical route to β2,3-amino acids with alkyl side chains

Luigi Longobardo1*, Marina DellaGreca1 and Ivan de Paola2

*Correspondence: luilongo@unina.it1 Dipartimento di Scienze Chimiche, Università degli Studi di Napoli Federico II, Via Cinthia 4, 80126 Naples, Italy

Full list of author information is available at the end of the articleOp



Abstract

en Access

Enantiopure N(Boc)-β3-amino nitriles, valuable synthetic intermediates in the multistep homologation of α-amino acids, were alkylated using n-BuLi as base. 

Alkylations afforded easily separable, almost equimolecular mixtures of diastereomeric N(Boc)-protected syn and anti β2,3-amino nitriles. 

Suitable manipulations of both cyano and amino groups eventually led to enantiopure N- and/or C-protected β2,3-amino acids. 

For example, methanolysis using conc. HCl gas in MeOH, provides C-protected β2,3 amino acids in excellent yields. 
This methodology is applied to the synthesis of a series N(Boc)-β2,3-dialkyl amino nitriles derived from L-phenylalanine, D-phenylalanine, L-valine and one C-protected β2,3 amino acid. 

We demonstrate an efficient procedure for the preparation of anti and syn β2,3-amino acids with alkyl side chains, from α-amino acids in reasonable yields.

Keywords: Beta-amino acids, Beta-amino nitriles, Alkylation, Homologation, Carbanions