Total Syntheses, Optical Rotations and Fragrance Properties of Sandalwood Constituents: (−)‐(<i>Z</i>)‐ and (−)‐(<i>E</i>)‐β‐Santalol and Their Enantiomers, <i>ent</i>‐β‐Santalene

Abstract

Abstract Enantiomerically pure 5‐norbornene‐2‐carboxylic acids 4 , obtained by asymmetric Diels‐Alder additions, were oxidatively degraded to (+)‐ and (−)‐2‐norbornanone [(+)‐, (−)‐ 21 ] and (+)‐ and (−)‐3‐methyl‐2‐norbornanone [(+)‐, (‐)‐ 11 ] which were converted into the title compounds by stereoselective alkylations, subsequent cis ‐ and trans ‐selective Wittig reactions and reductions. Precise optical rotations were determined for (Z)‐ and ( E )‐β‐santalol ( 1 and 2 ) and β‐santalene ( 3a ) which were obtained by total synthesis and, in addition, by isolation from East Indian sandalwood oil. magnified image