Diastereoselective Diels-Alder reactions of N-sulfonyl-1-aza-1,3-butadienes with optically active enol ethers: an asymmetric variant of the 1-azadiene Diels-Alder reaction.

The first detailed study of a room-temperature asymmetric Diels-Alder reaction of N-sulfonyl-1-aza-1,3-butadienes is reported enlisting a series of 19 enol ethers bearing chiral auxiliaries, with many providing highly diastereoselective (endo and facial diastereoselection) reactions, largely the result of an exquisitely organized [4+2] cycloaddition transition state. Three new, readily accessible, and previously unexplored auxiliaries rationally emerged from the studies and provide remarkable selectivities (two of these give 49:1 endo:exo and 48:1 facial selectivity) that promise to be useful in systems beyond those detailed.

Synthesis of the chlorofusin cyclic peptide: assignment of the asparagine stereochemistry.

An efficient synthesis of two diastereomers of the chlorofusin cyclic peptide bearing either the l-Asn3/d-Asn-4 or d-Asn3/l-Asn4 stereochemistry is detailed. Four key subunits were prepared, sequentially coupled, and cyclized to provide the two diastereomeric macrocycles. The absolute stereochemistry at the asparagine residues 3 and 4 was assigned as l and d, respectively, by correlating the NMR data of the two diastereomers with that reported for the natural product.

A short, highly efficient synthesis of coenzyme Q(10).

The most efficient synthesis reported to date of ubiquinone (CoQ10) is described. A sequence consisting of six operations is involved which leads to crystalline material in an overall yield of >64%.

On the verge of axial chirality: atroposelective synthesis of the AB-biaryl fragment of vancomycin.

[structure: see text] Using the "lactone concept", differently substituted AB-biaryl fragments (P)-2 (R = Me, t-Bu) of vancomycin have been synthesized atroposelectively. Their otherwise configurational instability was remedied by inclusion of two chlorine atoms in the B ring to give (M)-29. Starting from a still configurationally unstable lactone-bridged precursor, we obtained this biaryl with high atroposelectivity (dr 94:6) by ring cleavage with dynamic kinetic diastereomeric resolution.