M. Robert Leanna

Synthesis of α-amino and α-alkoxy aldehydes via oxoammonium oxidation

Abstract Oxoammonium oxidation (TEMPO, 1 ) of various optically active α-amino and α-alkoxy alcohols affords the corresponding aldehydes in good yield and high enantiomeric purity.

N-(Boc)-(L-(2-bromoallyl)-glycine : a versatile intermediate for the synthesis of optically active unnatural amino acids

Abstract N(Boc)-L-(2-Bromoallyl)-glycine ( 1 ) was synthesized from diethylacetamidomalonate and 2,3-dibromopropene in a one-pot procedure (75 % overall yield). The enantiomers were efficiently separated via a tandem biocatalytic kinetic hydrolytic resolution. 1 was elaborated to several other interesting unnatural amino acid.

Practical Method for Asymmetric Addition of Arylboronic Acids to α,β-Unsaturated Carbonyl Compounds Utilizing an In Situ Prepared Rhodium Catalyst

A new practical method for the asymmetric Michael addition of arylboronic acids to alpha,beta-unsaturated carbonyl compounds utilizing in situ generated chiral rhodium-binap-based catalyst has been developed to address the unavailability of the preformed catalysts. While maintaining high levels of enantioselectivity reported for the preformed catalysts, the new method provides a convenient access to either enantiomeric form of the product and allows for a substantial reductions in both the boronic acid and the catalyst loads.

Synthesis of α-halomethyl ketones: Oxidative hydrolysis of vinyl halides

Oxidative hydrolysis (e.g. aqueous NBS) of various vinyl halides affords the corresponding α-halomethyl ketones in good yield and purity.

The stereospecific preparation of an hydroxyethylene isostere precursor via a novel piperidine-2,5-dione template

Abstract Hydroxyethylene isostere precursor 2 was synthesized by stereochemical manipulation of a novel keto- lactam “template”. The final product was prepared in very high enantiomeric purity, in 23% overall yield from L- phenylalanine.

Diastereoselectivity in ergoline synthesis: a face selective epoxidation

Abstract Epoxidation of 1-Benzoyl-1,2,2a,3-tetrahydrobenz[ cd ]indole ( 4a ) proceeded smoothly with metachloroperbenzoic acid with high exo diastereoselectivity (de = 96%) and chemical yield (97%). The basis for this selectivity was probed with substituent effects, and was extended to other oxidation media.

Toward developing peptidomimetics: Successful replacement of backbone amide bonds in tetrapeptide-based CCK-A receptor agonists

Abstract The backbone amide bonds in two series of tetrapeptide-based CCK-A receptor agonists were systematically replaced with the methylene amino isostere. Potent and selective pseudopeptides were identified that will facilitate our understanding of how these peptides interact with the CCK receptor and their structural correlations with other CCK ligands. This information will aid in the eventual development of peptidomimetics.