An asymmetric synthesis of carboxylic acid derivatives, including lactic acid and α-amino acid derivatives, from optically active 1-chlorovinyl p-tolyl sulfoxides and ester lithium enolates with creation of chirality at the α-position

Abstract

Treatment of optically active 1-chlorovinyl p-tolyl sulfoxides, which were synthesized from symmetrical ketones or methyl formate and ( R)-(−)-chloromethyl p-tolyl sulfoxide in three steps, with lithium enolate of carboxylic acid tert-butyl esters gave optically active adducts having a substituent (alkyl, alkoxy, or dibenzylamino group) at the α-position with high 1,4-chiral induction from the sulfur chiral center. The adducts were converted to optically active esters, lactic acid, and α-amino acid derivatives having a chiral center at the α-position. When this addition reaction was carried out with an ester enolate generated from excess carboxylic acid tert-butyl ester with LDA in the presence of HMPA, the diastereomer of the adduct was obtained. By using the two reaction conditions for the generation of the ester enolate, a new method for asymmetric synthesis of both enantiomers of carboxylic acid derivatives having a substituent at the α-position from the one chiral source, ( R)-(−)-chloromethyl p-tolyl sulfoxide, was achieved.