Patent ID: 6906198

Claim:
A compound of formula: p is an integer of from 0 to 5; R 51 is H, alkyl, acyl, or aryl; R 52 , R 53 , and R 54 are each independently selected from H, hydroxyl, alkyl, acyl, and aryl, or any two of R 52 , R 53 , and R 54 together form ═O or ═C(R 57 )(R 58 ), where R 57 and R 58 are each independently selected from H, alkyl CO 2 (C 1 -C 6 ) alkyl, CON(C 1 -C 6 )alkyl, and CO 2 (aryl); and R 55 and R 56 are each independently H or a suitable protecting group for nitrogen.