18 セスキテルペンラクトン類の合成(III) : Vulgarin,Arglanine,Reynosin,Epoxysantamarine,および1β-Hydroxyarbusclin Aの合成

概要

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Eudesmane type sesquiterpenes possessing functional groups at C_1 and C_4 positions were synthesized from α-santonin in the following manner. I) Vulgarin were synthesized according to Scheme 1. Allyl rearrangement of 2a, followed by oxidation with Collins reagent gave 4. Ketalization of 4 and successive isomerization of double bond gave 6. Oxidation of 6 with OsO_4 gave ketal (7), (9) and ketone (8). Treatment of 7 and 8 with boiling 50% aq AcOH gave vulgarin. II) Arglanine was synthesized according to Scheme 2. Phenyl-selenylation of 7 and successive oxidative syn-elimination gave 11. Deketalization and spontaneous dehydration of 11 gave arglanine. III) Reynosin was synthesized according to Scheme 3. Bromination of 6 gave 12 by spontaneous dehydrobromination and deketalization. Reduction of 12 with zinc and acetic acid gave 13. Reduction of 13 with LiAlH(tBuO)_3 gave 14. Phenylselenylation of 14 followed by oxidative syn-elimination gave reynosin. IV) Epoxysantamarine was synthesized according to Scheme 4. Reductive dehydration of vulgarin and its C_4-epimer gave 16, which was reduced with LiAlH(tBuO)_3 to give 17. Epoxidation of 17 followed by phenylselenylation and syn-elimination gave epoxy-santamarine. V) 1β-Hydroxyarbusclin A was synthesized according to Scheme 5. Catalytic hydrogenation of vulgarin followed by reduction with NaBH_4 gave 21, which was converted to 1β-hydroxyarbusclin A.
天然有機化合物討論会の論文
1976-09-20