| abstract |
A compound of the formula wherein L is radical in which R 1 is hydrogen, optionally substituted alkyl, aryl, heteroaryl, aralkyl or cycloalkyl; R2 is hydrogen, hydroxy, optionally substituted alkyl, aryl, aralkyl, alkoxy, aryloxy, aralkoxy, alkylthio, arylthio or aralkylthio; R3 is hydrogen or aryl; or R2 and R3 combined are alkylene which together with the carbon atoms to which they are unique form a 5 to 7 member ring; n is zero or an integer from 1 to 2; And it is hydrogen; or Y and R2 taken together with the carbon atoms to which they are unique form a bond whenever n is 1; R4 is hydrogen. |