Ethyl glyoxylate equivalent. Lithiation, e.g. with lithium diethylamide, provides a useful 2-carbon fragment: Tetrahedron Lett., 4551 (1975). Reaction with the bis-Grignard from 1,4-dibromobutane gives 1-(diethoxymethyl)cyclopentanol: Canad. J. Chem., 66, 168 (1988).