Compounds of formula (I) wherein A has the meanings defined above with the proviso that A is not --NHCO-- may be prepared by reaction of the aldehyde (II) (wherein R has the meanings defined above in formula (I) or is protected derivative thereof, R4 is a carboxyl protecting group and R5 is a nitrogen protecting group), ##STR3## with the cyclic amide (III) (wherein R1 and A have the meanings defin