Dihydroxyacetone phosphate (DHAP)-dependent rhamnulose aldolases display an unprecedented versatility for ketones as electrophile substrates. We selected and characterized a rhamnulose aldolase from Bacteroides thetaiotaomicron (RhuABthet) to provide a proof of concept. DHAP was added as a nucleophile to several α-hydroxylated ketones used as electrophiles. This aldol addition was stereoselective and produced branched-chain monosaccharide adducts with a tertiary alcohol moiety. Several aldols were readily obtained in good to excellent yields (from 76 to 95 %). These results contradict the general view that aldehydes are the only electrophile substrates for DHAP-dependent aldolases and provide a new C-C bond-forming enzyme for stereoselective synthesis of tertiary alcohols.

Dihydroxyacetone phosphate(DHAP)-dependent rhamnulose aldolases display an unprecedented versatility for ketones as electrophile substrates. We selected and characterized a rhamnulose aldolase from Bacteroides thetaiotaomicron (RhuABthet) to provide a proof of concept. DHAP was added as a nucleophile to several -hydroxylated ketones used as electrophiles. This aldol addition was stereoselective and produced branchedchain monosaccharide adducts with a tertiary alcohol moiety. Several aldols were thus readily obtained in good to excellent yields (from 76 to 95%). These results contradict the general view that aldehydes are the only electrophile substrates for DHAP-aldolases and extend the chemists' toolbox to a new C−C bond-forming enzyme for stereoselective synthesis of tertiary alcohols.