ALKYLATION REACTIONS OF PROPARGYL ALCOHOL; IMPROVED ROUTES TO PROSTAGLANDIN α-SIDE CHAIN PRECURSORS

Article abstract of DOI:10.1016/S0040-4020(01)96065-X

Alkylation reactions of the dilithio derivative of propargyl alcohol and the lithio derivative of tetrahydropyranyl protected propargyl alcohol have been explored in order to develop improved synthetic routes to the key prostaglandin α-side chain precursor methyl 7-hydroxyhept-5-ynoate (5).The use of methyl 4-bromobutanoate or the lithium salt of 4-bromobutanoic acid in these reactions did not produce the required products whereas alkylation using trimethyl ortho-4-bromobutanoate (15) gave methyl 7-hydroxyhept-5-ynoate (5) or the corresponding THP ether (4) in good yield after orthoester hydrolysis.Procedures are also described for the transformation of alcohol (5) and THP (4) into methyl 7-bromohept-5-ynoate (1).Alcohol (5) can also be converted into methyl (Z)-7-bromohept-5-enoate (2) using literature procedures.