Patent ID: 7351389

Claim:
A compound of the formula wherein A 1 is —(CH 2 ) m ′ or a single bond; (CH 2 ) m and (CH 2 ) m ′ may independently be substituted with alkyl or hydroxyalkyl; R 1 and R 2 are each independently hydrogen or with the proviso that at least one of R 1 and R 2 must be other than hydrogen; R 3 and R 4 are independently hydrogen, alkyl, arylalkyl, aryl, alkoxy and hydroxyalkyl; R 12 is hydrogen, alkyl or hydroxyalkyl; R 13 is hydrogen, alkyl, arylalkyl, aryl, alkoxy or hydroxyalkyl; m and m′ are independently 1 to 5; and multimeric forms thereof.