P-13 ビシクロ[3.1.0]ヘキサン化合物の不斉合成とその求核的開環反応を利用した天然物の合成(ポスター発表の部)

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Bicyclo [3.1.0] hexane derivatives are of considerable importance in natural product synthesis due to the versatility of the cyclopropane ring and the ubiquitous occurrence of the cyclopentane ring in natural products. We wish to report asymmetric synthesis of bicyclo-[3.1.0] hexanes and their application to the natural products synthesis. 1. Asymmetric Synthesis of Bicyclo [3.1.0] hexanes. Chiral diazocarbonyl compounds (6e, 6f and 13) were prepared from methyl acetoacetate(5) and (R) or (S)- pantolactone. Diastereoselective intramolecular cyclopropanation of 6e, 6f and 13 using bis(oxazoline)copper (I) complexes or Rh_2(OAc)_4 as catalysts gave cyclopropanes (8e, 7f and 14) with 50-70% d.e. which were easily separated by simple silica-gel chromatography. Hydrolysis of 8e, 7f and 14 followed by esterification gave chiral bicyclo [3.1.0]-hexanes ((-)-3, (+)-3,and (-)-4). 2. Chiral Syntheses of Vitamin D_3 CD Ring Synthon, ent-Vitamin D_3 CD Ring Synthon and Formal Synthesis of (-)-Carbovir. Opening of enantiomerically pure (-)-3 and (+)-3 with cuprous iodide-mediated 4-methyl-pentylmagnesium bromide, followed by further synthetic modification, lead to (+)-vitamin D_3 CD ring synthon((+)-19) and (-)-ent-vitamin D_3 CD ring synthon((-)-19). Alcohol (24), an immediate precursor to anti-HIV agent (-)-carbovir was synthesized in 7 steps utilizing the addition of acetic acid to enantiomerically pure 14 as a key step. 3. Cleavage Reaction of Bicyclic Compounds and Synthesis of 22-Oxavitamin D_3 CD Ring Synthon and Formal Synthesis of (±)-epi-Juvabion. We found 3 was cleaved cleanly by various alcohols in the presence of boron trifluoride etherate and vitamin D_3 analogue, 22-oxavitamin D_3 CD ring synthon (30) was synthesized using that reaction. The optimized yield of addition of organocopper reagents to 3 was obtained using higher order cyano cuprate in the presence of trimethylsilylcyanide. The reaction was applied to the synthesis of (±)-epi-juvabion intermediate(36).
天然有機化合物討論会の論文
1995-09-01

P-13 ビシクロ[3.1.0]ヘキサン化合物の不斉合成とその求核的開環反応を利用した天然物の合成(ポスター発表の部)

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