Synthesis of sterically hindered chiral 1,​4-​diols from different lignan-​based backbones

Methods for synthetic modifications of the natural dibenzylbutyrolactone lignan hydroxymatairesinol into chiral 1,​4-​diols with different lignan-​derived backbones have been developed.  A stepwise procedure, involving alkylation and oxidn., was shown to be successful and several highly substituted 1,​4-​diols, e.g., I, were prepd.  One substituted butyrolactone intermediate resisted alkylation and led to the formation unusually stable hemiketals (butyrolactols) II (R = β-​Me, α-​Me)​.  The formation of stable hemiketals was investigated in detail, showing that different backbone structures influence the formation and reactivity of the hemiketals.