Lactone (+)-12 is envisioned as the precursor to the FGH rings of penitrem D (4) in our ongoing synthetic venture. The efficient, stereocontrolled introduction of the vicinal quaternary methyl groups present the major challenge in the construction of this subunit. Our first route to (f1-12 was marked by low overall yield (< 2% 1 and the instability of several key intermediates; these deficiencies were rectified in a second-generation approach that ...
[Hays, Sheryl J.; Novak, Perry M.; Ortwine, Daniel F.; Bigge, Christopher F.; Colbry, Norman L.; et al. Journal of Medicinal Chemistry, 1993 , vol. 36, # 6 p. 654 - 670]