Gold(I)-catalyzed enantioselective synthesis of benzopyrans via rearrangement of allylic oxonium intermediates.

The first transition metal catalyzed asymmetric carboalkoxylation reaction of propargyl esters is described. The (R)-MeO-DTBM-BIPHEP(AuCl)(2)-catalyzed reactions allow for the construction of benzopyrans containing quaternary stereocenters with excellent enantioselectivity. Experimental evidence supports a mechanism proceeding via the generation of a stabilized carbocation from an allylic oxonium intermediate and subsequent trapping by a chiral allylgold(I) spieces.

Selective synthesis of phosphate monoesters by dehydrative condensation of phosphoric acid and alcohols promoted by nucleophilic bases.

Phosphate monoesters are synthesized from a mixture of phosphoric acid (1 or 2 equiv) and alcohols (1 equiv) in the presence of tributylamine. The reaction is promoted by nucleophilic bases such as N-alkylimidazole and 4-(N,N-dialkylamino)pyridine. 2',3'-O-Isopropylidene ribonucleosides are selectively converted to their 5'-monophosphates without the protection of amino groups in nucleobases.