"H2CH2???, HOOCCH2???, HOOCCH2CH2???, H2NC(???O)CH2???, H2NC(???O)CH2CH2???, benzyl, para-hydroxy-benzyl, cyclohexyl, phenyl, p is 1, and wherein the configuration at CR7R8 can be R or S; if R7 is other than H, then R8 is preferably H; R6 is preferably H; if p is greater than one, R7 and R8 are preferably H;" . . . .