ppts etoh 2 lialh4 co2h oh 64 overall yield h h 143

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Unformatted text preview: ynthesis, 1996 OTBS 12 Total Synthesis of hirsutene PhSe PhSeCl, CH2Cl2, -78C O O (phenylselenolactonization) 140 O OTBS H 141 H H2O2 THF Ph O O O H selenoxide O Se syn elmination O H H 136 (62% from 138) H Ph 140 O H PhSe +Se PhSeCl PhSe O+ O OTBS H O OTBS OTBS H Kinzel, Organic Synthesis Workbook Cl- O H Nicolaou, Classics in Total Synthesis, 1996 13 Total Synthesis of hirsutene Br 42 THPO THPO O Li naphthalenide, THF, -78C (organo lithium formation); O H CO2H then CuBr SMe2 (organocuprate formation); then 136 (50-75%) H (SN2'-anti lactone opening) 136 H δ- THPO Br 2Li O δ+ THPO Li 42 δ+ 143 + BrLi CuBr SMe2 THPO Cu + O δ- H Less hindered side THPO 136 THPO O C CO2H H H 143 MSU online organic chemistry textbook +Cu O H H Nicolaou, Classics in Total Synthesis, 1996 14 THPO Total Synthesis of hirsutene HO 1.) PPTS, EtOH 2.) LiAlH4 CO2H OH (64% overall yield) H H 143 H H 144 1.) (CF3SO2)2O, pyr. CH2Cl2, -10C 2.) n-Bu4NI, PhH, reflux (64% overall yield) I 1.) Me3Si (1.0 equiv.), THF, 0C I Li I 2.) CsF (78% overall) H 134 The neopentyl iod...
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