Phorbol 1-The Oxidopyrylium Approach Cyclizations with 5-Hydroxy-4-Pyrones A=8 Phorbol 1)PhH, reflux, 12 h 2:1 erythro: threo DBU, RT 1)CH3CN, reflux, 60 h t-BuLi nder, et. al. J. Am. Chem nder. et. al. J. Am. chem 7-8958 Phorbol 35B-06 Ylides3/16/934:45PMGarst, M. E.; McBride, B. J.; Douglass, J. G. III. Tetrahedron Lett. 1983, 24, 1675-1678. n = 1 : 70% n = 2 : 65% Z = CO2Me 1) heat 2) acetylation 42% 55% 1) CH3CN,reflux, 60 h 2) acetylation 1) PhH, reflux, 12 h 2) acetylation Cyclizations with 5-Hydroxy-4-Pyrones * * 92% Phorbol 1 - The Oxidopyrylium Approach Phorbol 2:1 erythro : threo 2:1 epimers DBU, RT t-BuLi Phorbol Wender, et. al. J. Am. Chem. Soc. 1989, 111, 8954-8957. Wender, et. al. J. Am. Chem. Soc. 1989, 111, 8957-8958. - + OH OH H OH OH OH H O O O OAc OTBS OAc O H OAc O OTBS OAc H OTBS O O O I O O H O H O O OPiv OH O H O H OH O OH O A B O O OH A B O O OH N O O O OH N O O N O O OAc H O N O O OAc O O OH ( )n Z Z O ( )n Z O OAc Z H 35B-06 Ylides 3/16/93 4:45 PM