Pergamon Tetrahedron Letters, Vol. 38, No. 33, pp. 584%5850,1997 © 1997 Elsevier Science Ltd All rightsreserved.Printed in Great Britain 0040-4039/97 $17.00+ 0.00 PII: S0040-4039(97)01300-2 Stereoselective Sulfoxide Directed Reduction of 1,2-Diketo-Derivatives to Enantiomerically Pure Syn and Anti 1,2-Diols. Guy Solladi~*, Giiles Hanquet, Catherine Roiland Laboratoire de St~r~ochhnle as~oci~ au CNRS, ECPM, Uuiversit~ Louis Pasteur 1 rue Blaise Pascal, 67008-Strasbourg, France Abstract: A new route to enantiopure syn and anti 1,2-diols is described from oxalyl-di-(N- methyl-N-methoxyamide) via the corresponding ~-ketosulfoxide.This is the first report of the stereoselectivereductionofaT--keto-~-hydroxysulfoxide.© 1997 Elsevier Science Ltd. In the course of our studies concerning sulfoxide-directed reduction of carbonyl groups, we have shown that enantiomerically pure syn and ant/1,2-diols could be obtained by reduction of [5-keto-7-hydroxysulfoxides easily made from ¢x-hydroxyesters.1 We report now the synthesis of enantiomerically pure syn and anti 1,2-diols 6 from the oxalic acid derivative 1 using a new highly diastereoselective reduction of a carbonyl (>95/5 to >97/3) directed by a sulfoxide in 7-position (scheme 1). The di-N-methyl-N-methoxyamide of oxalic acid 12, reacted smoothly with (+)R p-tolylmethyl sulfoxide anion3 to give in 78% isolated yield the [5-ketosulfoxide (R)-2.4 The DIBAL reduction of the I~--ketosulfoxide 2 provided then the I~-hydroxysulfoxide 35 with high S-diastereoselectivity (>97/3) and 81% isolated yield, thus showing that there was no significant effect of the vicinal amide function.6 The protected ~-hydroxysulfoxide (R,S)-4 was transformed, by Grignard addition to the Weinreb amide7, into the [~-hydroxy-7-ketosulfoxide 5(a-d) in good to excellent yields (78 to 92%). The S absolute configuration at the C-2 chiral center in compound 5, deduced from our previous results and model of approach s for the reduction step, was confirmed by chemical correlation of 5b to the known (+)(R) 1-phenyl-2- hydroxypropanone 79 by desulfurization and deprotection. DIBAL reduction of the [~-silyloxy 7-ketosulfoxide 5a happened to be a slow process requiring 12h to afford a moderate yield (60%) of the desired syn diol 6a with a low diastereoselectivity (75%), Table I. We discovered that addition of a Lewis acid, having no tendency to chelate, allowed to carry out the reaction in a • Fax : (33) 3 88 61 65 31. e-mail : solladie@chimie.u-stmsbg.fr 5847