The present invention relates to a compound of formula (XX): wherein R 3 is lower alkyl, optionally substituted phenyl or optionally substituted naphthyl. Y each independently is halogen, C 1-4 -alkyl, C 1-4 -haloalkyl, C 1-4 -alkoxy, C 1-4 -haloalkoxy, phenyl, cyano or nitro； m is 0-5； and A is N or CH； And to a method for producing the same, comprising converting a 2,2-bishydroxymethyl cyclopentanol derivative of formula (XIX) wherein A, Y and m are as defined in claim 1, into an oxetane ring while converting into a sulfone ester.
