Construction of intermediate 86 1. Ac2O(excess), pyr, 25C 2. allyltrimethylsilane, BF3 OEt2 1.m2C=s,PhcH3110°c TMSOTf, CH3CN,0C 2. n-Bu3SnH, AIBN(cat) 3. NaoMe,MeOH,25° 5% 4.4-BuPha SiCl imid. DMF0C 79. D-mannose en 2-methoxypropene CSA(cat ),0C (82%) 1. amberlyst-15(H") MeH,60°c(72%) DMF,1009(74%) OTPS AlMe3, MgBr2 OEt2 (COCl2, DMSO, H2Ch, 78C (61% Yield of 91 enEN.0°c OTPS (100%Yed) 114 1.03,CH2Ch2-780 2cH2 CHMgBr,TFH,0° DMF. 25.C (44% Yield) TPS 2 O3, CH2Cl2,-78C (ca. 1: 1 mixture of 3. Ph3P=CHCO2I (ca. 3: 1 mixture of 25 (78% overallConstruction of Intermediate 86 HO O OH OH HO OH 79: D-mannose O OH O O H OTPS 1. Ac2O (excess), pyr., 25 oC 2. allyltrimethylsilane, BF3 OEt2 , TMSOTf, CH3CN, 0 oC 3. NaOMe, MeOH, 25 oC (75% overall) 4. t-BuPh2SiCl, imid., DMF, 0 oC; then 2-methoxypropene, CSA (cat.), 0 oC (82%) 112 1. Im2C=S, PhCH3 , 110 oC 2. n-Bu3SnH, AIBN (cat), PhCH3 , 110 oC (66% overall) O O O H OTPS 113 1. amberlyst-15 (H + ), MeOH, 60 oC (72%) 2. n-Bu2SnO, MeOH, 60 oC; then BnBr, DMF, 100 oC (74%) O HO BnO H OTPS 114 (COCl)2 , DMSO, CH2Cl2 , -78 oC; then Et3N, 0 oC (100% Yield) O H O O H OTPS M L L Ph Nu O O BnO H OTPS 115 AlMe3 , MgBr2 OEt2 , CH2Cl2 , -50 oC (61% Yield of 91) O HO H OTPS 91 Me OBn K (ca. 3:1 mixture of diastereomers) 1. O3 , CH2Cl2, -78 oC; then Me2S, Ph3P 2. CH2=CHMgBr, TFH, 0 oC (44% Yield) O HO OTPS 117 Me OBn K HO H H (ca. 1:1 mixture of diastereomers) O HO OTPS 90 Me OBn K TPSO H H CO2Me 1. t-BuPh2SiCl, imid., DMF, 25 oC 2. O3 , CH2Cl2 , -78 oC; then Me2S, Ph3P 3. Ph3P=CHCO2Me, PhH, 25 oC (78% overall)