Stereoselective total synthesis of (+/-)-thielocin A1beta.

The stereospecific total synthesis of (+/-)-thielocin A1beta has been achieved from the common intermediate ethyl 5-formyl-2,4-dihydroxy-3,6-dimethyl benzoate (8). The racemic synthesis was achieved based on the key reaction of a 4-methyl-3,4-dihydroxy cyclohexadienone 38 with a quinone methide derived at low temperature from the fluoride ion catalyzed composition of piperidinium salt 40. The resulting condensate (31) was homologated by successive esterification with protected monomeric phenol 41 to provide, after careful removal of the protecting groups, the desired thielocin A1beta.