Abstract: The present invention provides an efficient synthetic method of &agr;-ketol unsaturated fatty acid having a double bond at a &bgr;-position to the ketone group thereof. It comprises the steps of: preparing compound (4) by reacting monosubstituted acetylene (2) with epoxide (3); and preparing &agr;-ketol unsaturated fatty acid (1) from said compound (4) as shown in Reaction Formula 1: wherein R1 represents an alkyl group of 1-18 carbon atoms or an aliphatic hydrocarbon group of 2-18 carbon atoms having 1-5 double or triple bonds at given positions; R2 represents a protecting group for a hydroxyl group; R3 represents a protecting group for a carboxyl group; R is identical to R1 or, when R1 has one or more triple bonds, represents an aliphatic hydrocarbon group in which each triple bond of R1 is converted to a double bond; and A represents an alkylene group of 1-18 carbon atoms.

Abstract: The present invention provides an efficient synthetic method of &agr;-ketol unsaturated fatty acid having a double bond at a &bgr;-position to the ketone group thereof.

Abstract: The present invention relates to an oxetane derivative represented by the general formula (I): ##STR1## wherein R.sub.1 and R.sub.2 are each an acyl group and R.sub.3 is a hydrogen atom or a lower alkyl group, which is useful as an intermediate for the preparation of a compound having a (bishydroxymethyl)oxetane structure in its saccharide moiety, for example, oxetanosine, and a process for the preparation of the same.