HIGHLY STEREOSELECTIVE SYNTHESIS OF THE ANTIPLATETLET ACTIVATING FACTOR, 4-THIAZOLIDINONES, USING SILYL DERIVATIVES OF 2-MERCAPTOALKANOIC ACIDS

The cycle-condensation of silyl 2-mercaptoalkanoates and arylmethylene amines proceeded with high stereoselectivity to give alternatively bot h the cis- and trans-2,5-disubstituted 4-thiazolidinones, some of whic h are known as anti-platelet activating factor-active drugs. The use o f the piperidine catalyst and no catalyst showed very high cis-stereos electivity (cis/trans=10/1-50/1) during the reaction. On the other han d, the trans-selective reaction was promoted by Ti(O-i-Bu)(4) and Al(O -s-Bu)(3) catalysts (cis/trans=1/8-1/25). Both reactions were conducte d with higher cis- and trans-selectivities as compared with those of t he alkyl 2-mercaptoalkanoates under mild conditions. The cycle-condens ation using trimethylsilyl 2-(trimethyl-silylthio) propionate and meth yl 2-(trialkylsilylthio) propionates proceeded by the action of a cata lytic amount (0.02 molar amount) of tetrabutylammonium fluoride with m oderate cis-selectivity.