An efficient asymmetric synthesis of anti-1,2-disubstituted taurine derivatives through nucleophilic addition of phenylmethanesulfonate to various N-acylimines in the presence of 1,2:5,6-di-O-isopropylidene-a-D-allofuranose as a chiral auxiliary is described. The taurine derivatives were obtained in three steps with good overall yields (36-61%) and excellent enantiomeric excesses (83-98%). The diastereomeric excesses of 15-91% could be improved to 90-98% by column chromatography or recrystallization. The relative and absolute configurations of the products were determined by means of an X-ray crystal structure analysis.Sulfonic acids and their derivatives are important biologically active constituents of mammals, marine algae, fish, and shellfish. 1 The best known are 2-aminoethanesulfonic acid (taurine) and related compounds such as 3-aminopropanesulfonic acid (homotaurine), 2-carbamimidamidoethanesulfonic acid (N-guanidinotaurine), cysteic acid, and 2-hydroxyethanesulfonic acid (isethionic acid) ( Figure 1). Taurine is found in relatively high concentrations in the central nervous system, brain, heart, retina, and muscles, and is involved in various physiological processes such as brain development, neurotransmission, and immunomodulation. 2In view of the important physiological effects of these naturally occurring aminosulfonic acids, which can be regarded as sulfur analogues of amino acids, the development of new diastereo-and enantioselective methods for their synthesis is highly desirable.Several reports have already been devoted to the synthesis of taurine derivatives. 1-Substituted taurines have been synthesized from olefins, 3 from b-amino secondary alcohols, 4 and from epoxides. 5 2-Substituted taurines have been prepared from b-amino primary alcohols, 6 from aziridines, 7 and from 2-nitroalkanesulfonic acids. 8 1,1-Disubstituted taurines are available from ketones through Corey-Chaykovsky epoxidation, episulfidation, and ammonia-induced ring cleavage, followed by oxidation with performic acid. 9 1,2-Disubstituted taurines have been prepared from olefins 9,10 and from epoxides. 5 2,2-Disubstituted taurines have been synthesized from aziridines, 11 from amino alcohols, 6f and from ketones through the Strecker amino acid synthesis. 12Our group has described an efficient asymmetric synthesis of 2-substituted and 1,2-disubstituted taurine derivatives through aza-Michael addition of the enantiopure hydrazines (2S)-2-(methoxymethyl)pyrrolidin-1-amine (SAMP) or (2R,3aR,6aR)-2-(methoxymethyl)hexahydrocyclopenta[b]pyrrol-1(2H)-amine (RAMBO) to a,b-unsaturated sulfonates in the presence of a Lewis acid catalyst. 13In our ongoing research on the asymmetric synthesis of sulfonic acid derivatives, we planned to gain access to 1,2-disubstituted taurine derivatives through nucleophilic addition to an N-acylimine of a chiral phenylmethanesulfonate bearing an enantiopure sugar auxiliary.In previous communications and a full paper, 14 we reported on efficient asymmetric electrophilic a-substitution reactions of various a...