In the presence of a catalytic amount of VO(acac) 2 , oxidative coupling of 2-naphthol or phenol derivatives with molecular oxygen occurred at room temperature and selectively gave the corresponding ortho-ortho coupling products in moderate to high yields.

We report here the development of chemoenzymatic methods for the large-scale synthesis of cancer-associated antigens globopentaose (Gb5), fucosyl-Gb5 (Globo H), and sialyl-Gb5 (SSEA4) by using overexpressed glycosyltransferases coupled with effective regeneration of sugar nucleotides, including UDP-Gal, UDP-GalNAc, GDP-Fuc, and CMP-Neu5Ac. The enzymes used in the synthesis were first identified from different species through comparative studies and then overexpressed in E. coli and isolated for synthesis. These methods provide multigram quantities of products in high yield with only two or three purification steps and are suitable for the evaluation and development of cancer vaccines and therapeutics.

No abstract

Optically active cyanohydrins are synthetic precursors of R-hydroxy carboxylic acids, R-amino carboxylic acids, β-hydroxy amines, and several other classes of organic compounds of biological importance. Existing methods for the preparation of chiral cyanohydrins include both enzymatic 1,2 and chemical processes. 1,3 Chemically, several efficient methods have been developed. In most of these methods, however, the chiral ligands are rather unstable and cannot be easily recovered. We now describe a new chiral Ti(IV) catalyst with dihydroxy-trans-1,2-diamide 3a as the ligand, which effects the enantioselective addition of trimethylsilyl cyanide to aldehydes.Ligand 3a and its diastereoisomer 3b were prepared from ketopinic acid chloride (1) 4 according to the Scheme 1. On treatment with optically pure (+)-or (-)-trans-1,2-diaminocyclohexane in dichloromethane in the presence of triethylamine, ketopinic acid chloride was converted to the trans-diketoamide 2a or 2b, respectively. Diketoamide 2a and 2b could also be obtained in pure form by reacting ketopinic acid chloride with (+)-trans-1,2-diaminocyclohexane in the same fashion as above followed by separation of the resulting diastereomeric mixture by column chromatography on silica gel. Subsequent reduction of 2a and 2b using L-selectride in tetrahydrofuran at -78 °C for 1 h and then at room temperature for 2 h gave 3a and 3b, respectively with the hydroxy group at the exo position. 5 The absolute stereochemistry of ligand 3a was further determined by X-ray crystallographic analysis. Ligand 3a was found to be an useful chiral ligand for asymmetric induction (eq 1). In conjunction with titanium tetraisopropoxide, ligand 3a was shown to effect the enan-

A facile VO(acac)(2)-catalyzed in situ generation of iminium ions from amine N-oxides and their participation in a modified Mannich-type reaction is described.