Patent ID: 6964976

Claim:
A compound of formula (La) or (Lb): wherein: R 1 and R 2 are the same or different and each represents a hydrogen atom or an amino protecting group; R 3a represents a hydrogen atom or a hydroxy protecting group or when R 1 is a hydrogen atom; R 2 and R 3a taken together form a group of formula —(C═O)—; R 4a represents a C 1 -C 20 alkyl group, a C 2 -C 20 alkyl group interrupted with a heteroatom(s), a C 1 -C 20 alkyl group substituted with an aryl group(s) or a heteroaryl group(s), a C 2 -C 20 alkynyl group, a C 3 -C 20 alkynyl group interrupted with a heteroatom(s), a C 2 -C 20 alkynyl group substituted with an aryl group(s) or a heteroaryl group(s), a C 2 -C 20 alkenyl group, a C 3 -C 20 alkenyl group interrupted with a heteroatom(s), a C 2 -C 20 alkenyl group substituted with an aryl group(s) or a heteroaryl group(s), a C 2 -C 20 alkyl group which is substituted with an aryl group(s) or a heteroaryl group(s) and interrupted with a heteroatom(s), or a cycloalkyl group; m represent an integer from 0 to 4; Ar represents an aryl group, a heteroaryl group, an aryl group substituted with 1 to 5 substituents selected from substituent group a, a heteroaryl group substituted with 1 to 5 substituents selected from substituent group a, with the proviso that when Ar is an aryl group, R 1 is not a hydrogen atom and R 2 and/or R 3a do not represent a hydrogen atom; wherein substituent group a represents a halogen atom, a lower alkyl group, a halogenated lower alkyl group, a lower alkoxy group, a lower alkylthio group, a carboxyl group, a lower alkoxycarbonyl group, a hydroxyl group, a lower aliphatic acyl group, an amino group, a lower mono-alkylamino group, a lower di-alkylamino group, a lower aliphatic acylamino group, a cyano group, and a nitro group.