"is [0313] Q is a bond and R1 is ???O???CH2???CH(OH)???; Q is a bond and R1 is ???CH(OH)???(CH2)2???; or Q is a bond and R1 is ???CH(OH)???CH2???S(O)0-2???. [0314] Preferred variables for G and G1 groups of the formulae [0315] are as follows: [0316] R2, R3, R4, R5, R6 and R7 are independently selected from the group consisting of H, (C1-C6)alkyl, benzyl and acetyl. [0317] Preferred variables for gr" . . . . .