ENANTIOMERICALLY PURE 7-OXABICYCLO[2.2.1]HEPT-5-EN-2-YL DERIVATIVES (NAKED SUGARS) AS SYNTHETIC INTERMEDIATES .11. TOTAL SYNTHESES OF (-)-CONDURITOL-B ((-)-1L-CYCLOHEX-5-ENE-1,3/2,4-TETROL) AND OF (+)-CONDURITOL-F ((+)-1D-CYCLOHEX-5-ENE-1,2,4/3-TETROL) - DETERMINATION OF THE ABSOLUTE-CONFIGURATION OF (+)-LEUCANTHEMITOL

The ‘naked sugar’ (+)‐(1R,2R4R)‐2‐endo‐cyano‐7‐oxabicyclo[2.2.1]hept‐5‐sn‐2‐exo‐yl acetate ((+)‐4) was converted (7 steps, 45% overall) with high stereoselectivity into (−)‐(4R,5S,6R)‐4,5,6‐tris{[(tert‐butyl)dimethylsilyl]oxy}cyclohex‐2‐en‐1‐one ((−)‐11). Reduction of (−)‐1 with NaBH4‐ CeCl3 · 7 H2O, followed by deprotection of the silyl ether moieties gave (+)‐conduritol F ((+)‐1; 47%) whose characteristics were identical to those of natural (+)‐leucanthemitol. Reduction of (−)‐11 with DIBAH, followed by deprotection of the silyl ether moiety led to (−)‐conduritol B ((−)‐3; 51 %). Copyright © 1990 Verlag GmbH & Co. KGaA, Weinheim