| 摘要 |
This invention provides a process for the preparation of the compounds of the formula (I): <CHEM> and salts and esters thereof wherein R<1> is a hydrogen atom, a lower alkyl group, a lower alkenyl group, a phenyl group or a phenyl-(lower alkyl) group; and R<2> is a hydrogen atom, a lower alkyl group, or a CH2OR<3> group where R<3> is a hydrogen atom, a lower alkyl group, a phenyl group, a phenyl-(lower alkyl) group or a lower acyl group, or R<1> is joined to R<2> to form the residue of a 5-7 membered saturated carbocyclic ring; which process comprises the reaction of an ester of clvaulanic acid with a compound of the formula (II): <CHEM> wherein R<1> and R<2> are as defined in relation to formula (I), and thereafter, if desired, de-esterifying the thus-produced ester to form the free acid or a salt. |
