"A highly diastereoselective and enantioselective epoxidation of aldehydes with diazoacetamides has been developed with mesoborate ester catalyst of VANOL. A wide range of aromatic and aliphatic aldehydes could be employed in this method to afford the cis-3,4-epoxy amides with good to excellent ee (67 to >99% ee) in good to excellent yield (47 to 99%). The synthetic application was demonstrated by the synthesis of the sidechain of taxol (6 steps, 63% overall yield). Based on the non-linear effect studies, the mesoborate catalyst was proposed to consist of two VANOL ligands in contrast to one for boroxinate catalyst, which was also effective for the same reaction. The mode of activation for aldehydes was proposed to be via a Lewis acid catalysis mechanism, supported by NMR studies. The mesoborate catalysts were found to be also effective in hetero-Diels-Alder reaction of aldehydes with Danishefsky's diene, aziridination reaction of imines and ethyl diazoacetate and three-component Passerini reaction of aldehydes. A simple and efficient chiral resolution of VANOL/BINOL/VAPOL and their derivatives via the spiroborate formation with quinine/quinidine has been developed. This method can be applied to 18 different ligands, including 9 new ligands such as 5,5'-, 3,3'- and 7,7'-substituted VANOLs. Optically pure ligands could be obtained in up to 47% yield (50% maximum). These ligands are thought to be useful in optimization and mechanistic investigation of various asymmetric reactions."--Page ii.
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