Syntheses and properties of optically active 2-substituted taurines

Abstract

The synthesis of nine 2-substituted taurines (5a–i), including the marine natural product D-cysteinolic acid (5f), are described. These involve the successive conversion of N-t-butoxycarbonyl(Boc)-protected amino acid esters (1) into the N-Boc-2-aminoethanols (2), their O-mesylated derivatives (3), the deprotected 2-aminoethyl methanesulphonates (4), followed by the replacement of the mesyloxy group by a sulpho group to give the optically active taurines (5a–e,g–i). Hydrogenolysis of 2-benzyloxymethyltaurine (5e) gives D-cysteinolic acid (5f). The structure of another of the products, (5b), is also confirmed by an alternative synthesis from N-Boc-valine methyl ester (1b)via two β-bromoethylamine derivatives, (6b) and (7b).