mula 9 wherein each R3 is independently an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, or a heteroaryl group; or further wherein R1 is a group of formula 10 wherein R4 and each R5 independently are an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, or a heteroaryl group; and X is OH; OR7, wherein R7 is alkyl or aryl; halogen; pseudohalogen; O