Abstract: A compound of the formula: ##STR1## wherein R.sub.1 is a hydrogen atom or a lower alkyl group, R.sub.2 is a hydrogen atom or a conventional protecting group for a carboxyl group, R.sub.0 is a hydrogen atom or a conventional protecting group for a hydroxyl group, X is a protected or unprotected amino group, a carboxyl group, a lower alkoxycarbonyl group, an ar(lower)alkyloxycarbonyl group, a cyano group, a hydroxyl group, a lower alkyloxy group, a lower alkylthio group, a lower alkylsulfonyl group or a group of either one of the following formulas: ##STR2## wherein R.sub.3 and R.sub.4, which may be the same or different, each represents a hydrogen atom or a lower alkyl group, or they are taken together to represent an alkylene chain to form, in combination with the adjacent nitrogen atom, a 3- to 7-membered cyclic amino group,--ZCOR.sub.5 (2)wherein Z represents --NH-- or --O-- and R.sub.