Application of [Mo2(OAc)4] for determination of absolute configuration of brassinosteroid vic-diols by circular dichroism

Abstract

The in situ complexes of dimolybdenum tetraacetate [Mo2(OAc)4] with vicinal diols give CD spectra suitable for determination of their absolute configuration. Positive (negative) torsional angle in the O-C-C-O moiety leads to a positive (negative) Cotton effect at around 300 nm. The extension of this rule to compounds containing a second vic-diol moiety in the same molecule is studied on brassinosteroid vic-diols 1–14. It is demonstrated that the in situ method allows fast and easy configurational assignment of both glycol moieties present in brassinosteroids on the basis of the sum and difference CDs of respective pairs of (22S,23S)- and (22R,23R)-isomers. Chirality 9:578–582, 1997. © 1997 Wiley-Liss, Inc.