Compactin lactone synthon

The arrangement of functional groups as well as the erythro configuration of the latent diol makes carbonate 517 an excellent candidate as a compactin lactone synthon (99) and it has in fact been used in the synthesis of both compactin (97) and mevinolin (98) (Scheme 75) [112]. 

In model studies related to the synthesis of compactin (97) and mevinolin (98), the upper-half lactone moiety was constructed from 550 starting with an oxirane ring-opening reaction by vinyl Grignard reagent (Scheme 81) [136]. lodocarbonation of 560 followed by hydrolysis and ketalization affords isomerically pure acetonide 562, the compactin lactone synthon. 

Compactin rely on a Diels-Alder strategy. An intermolecular version has diene (468) as the key synthon and suffers from a poor yield in the final demethylation step whereas an intramolecular approach using the aldehyde (469), derived from tri-O-acetyl-D-glucal, as the lactone synthon suffers from no such drawback at the... 

---