Isopropyl, ethyl, and methyl 2-(2-benzothiazolylsulfinyl) acetates have been found to be useful synthetic reagents for sulfinyl-Knoevenagel reaction with various aldehydes to give directly the corresponding 4-hydroxyalk-2-enoates [R′ CH (OH) CHCHCO2R], which are ubiquitous structures in biologically active natural products and useful building blocks for organic synthesis of chiral compounds. From the optically pure (R)-2-(2- ...