Overman: Laurenyne Synthesis ()-Laurenyne 1.(+)-DET, Ti(OiPr)4. IBuoOH 4A sieves.78% 3:1 regioselectivity, 92% 3. TsCl, pyridine, 88 H2 C2,98% OTBDPS 2equv).0°c,cH2Cl2 48 1. HF, pyridine, rt PCC, NaOAC, CHzClz 1-3 NaCN.DMso.95°c 32C-043/18999:54PM JAcs,1988,110.2248Overman: Laurenyne Synthesis JACS, 1988, 110, 2248 O Cl Me (-)-Laurenyne O Cl OTs HO Cl OTs O TMS Cl OTs EtO OTBDPS TBDPSO OEt TBDPSO PPTS (cat.) CH2Cl2, 98% 1. SnCl4 (2 equiv.), 0 °C, CH2Cl2 2. TBAF 37% yield, one isomer, 4 g scale OH 1. (+)-DET, Ti(OiPr)4, tBuOOH 4 Å sieves, 78% 2. Et3NHCl, Ti(OiPr)4, CH2Cl2 3:1 regioselectivity, 92% 3. TsCl, pyridine, 88% TMS TMS Overman: Laurenyne Synthesis JACS, 1988, 110, 2248 O Cl Me (-)-Laurenyne O Cl OTs TBDPSO O Cl OTs O H O Cl OTs Me 1. HF, pyridine, rt 2. PCC, NaOAc, CH2Cl2 3. TMSOTf, Et3N, 0 °C, Pd(OAc)2, CH3CN 56% 1. DIBAL 2. MsCl, Et3N 3. NaBH4, HMPA 65% 1. NaCN, DMSO, 95 °C 2. DIBAL 3. TIPS TIPS n-BuLi, HMPA THF, -78 °C 3:1 E:Z 4. TBAF 20 steps, 0.6% yield from 1,1-TMS-Br-ethylene 32C-04 3/18/99 9:54 PM