Heterocyclic compounds of formula, wherein R1 is carboxy or protected carboxy, R2 is aryl which may have suitable sustituent, R3 is aryl which may have suitable substituent, R4 is hydrogen, lower alkyl, hydroxy or aryl, A1 is lower alkylene, is, etc. The attachment has two side arms emanating from a center. The cartridge supporting assembly may be responsive to firing and retraction motions applied thereto from a firing assembly. The transformations may be in a number of homographic ways, including via translation, rotation, and scaling.