Compound of Formula IIo (Formula IIa where R15, R16 and R17 are H, R41 is P, R43 is C(OH)(CH2)0-3R1) is prepared by reacting compound of Formula IId (Formula IIa where R15, R16 and R17 are H, R41 is P, and R43 is a halogen, R59, e.g. chloro) with an organolithium reagent (e.g. butyllithium) to effect the lithium-halogen exchange at reduced temperature (e.g. ???78??? C.) in an appropriate solvent (