E. Marotta et al., PURE ENANTIOMERS OF BICYCLO[3.2.0]HEPT-3-EN-6-ONES AND BICYCLO[3.2.0]HEPT-3-EN-6-ENDO-OLS - RESOLUTION, ABSOLUTE-CONFIGURATION AND OPTICAL-PROPERTIES, Tetrahedron : asymmetry, 6(9), 1995, pp. 2319-2328
Single crystal X-ray diffraction analysis of compounds A, B and, C hel
ped us to assign the absolute configurations of the enantiomers of the
bicycle [3.2.0]hept-3-en-6-endo-ols 4-6. These bicyclic alcohols were
easily obtained by: (i) stereoselective reductions of the bicyclo[3.2
.0]hept-3-en-6-ones 1-3, (ii) conversion into diastereoisomeric pairs
using (-)-(1S,4R)-camphanic acid chloride as resolving agent, (iii) an
efficient separation of diastereoisomers by flash-chromatography and,
finally, (iv) a mild alkaline hydrolysis. The oxidation of pure enant
iomers of the bicyclo[3.2.0]hept-3-en-6-endo-ols 4-6 with tetra-n-prop
ylammonium perruthenate (TPAP) and N-methylmorpholine N-oxide (NMO) as
co-oxidant furnished enantiomerically pure bicyclo[3.2.0]hept-3-en-6-
ones 1-3. The different mutual disposition of carbonyl groups in the s
tructure A and B justifies the different IR (KBr) signals for the carb
onyls of each diastereoisomer.