Biomedical subjects

Brian C Shook

Publications and source records attributed to Brian C Shook.

3 recordsLinked to original sources

PubMed2002

A practical enantioselective total synthesis of the bengamides B, E, and Z.

[reaction: see text] A practical total synthesis of Bengamides B, E, and Z from a common polyol intermediate is described. Consecutive aldol condensations afford a protected polyol thioester side chain suitable for coupling to the Bengamides. A novel chiral phase transfer catalyzed enantioselective alkylation affords the more highly functionalized amino caprolactams required for Bengamides B and Z. Use of the 2-naphthylmethyl ether protecting group, compatible with the boron Lewis acids required for enantioselective aldol condensation, allows direct access to Bengamide B.

Antineoplastic Agents↗

PubMed2002

Unsaturated nitriles: stereoselective MgO eliminations.

Alpha,beta-unsaturated nitriles are readily synthesized by eliminating MgO from beta-hydroxynitriles. Deprotonating acyclic, and cyclic, beta-hydroxynitriles with excess MeMgCl smoothly generates dianion intermediates that eject MgO with concurrent formation of alpha,beta-unsaturated nitriles. Alternatively, sequential addition of lithioacetonitrile and MgBr(2) to aldehydes and ketones generates magnesium alkoxides in situ that eliminate MgO upon addition of MeMgCl. The MeMgCl-induced MgO eliminations smoothly generate alpha,beta-unsaturated nitriles from hindered ketones that are otherwise difficult to synthesize.

Aldehydes↗

PubMed2002

Nitrile anions: solvent-dependent cyclizations.

Extensive cyclizations in hydrocarbon and polar solvents demonstrate a profound solvent sensitivity for intramolecular nitrile anion alkylations. S(N)i cyclizations enforce very precise steric constraints in the transition state, allowing correlation of the cyclization stereochemistry with the orbital orientation of the nitrile anion. Collectively the cyclizations suggest a continuum of nitrile anion transition states, varying from planar to fully pyramidal, that selectively cyclize to cis- and trans-decalins, respectively.

Anions↗