Absolute stereochemistry of altersolanol a and alterporriols

The absolute stereochemistry of altersolanol A ( 1 ) was established by observing a positive exciton couplet in the circular dichroism (CD) spectrum of the C3,C4‐ O ‐bis(2‐naphthoyl) derivative 10 and by chemical correlations with known compound 8 . Before the discussion, the relative stereochemistry of 1 was confirmed by X‐ray crystallographic analysis. The shielding effect at C7′‐OMe group by C1‐ O ‐benzoylation established the relative stereochemical relationship between the C8‐C8′ axial bonding and the C1‐C4/C1′‐C4′ polyol moieties of alterporriols E ( 3 ), an atropisomer of the C8‐C8′ dimer of 1 . As 3 could be obtained by dimerization of 1 in vitro, the absolute configuration of its central chirality elements (C1‐C4) must be identical to those of 1 . Spectral comparison between the experimental and theoretical CD spectra supported the above conclusion. Axial stereochemistry of novel C4‐ O ‐deoxy dimeric derivatives, alterporriols F ( 4 ) and G ( 5 ), were also revealed by comparison of their CD spectra to those of 2 and 3 . Chirality, 2012. © 2011 Wiley Periodicals, Inc.