Francis K. Duah

A model for the enzyme-catalyzed, coenzyme B12-dependent interconversion of β-methylaspartate with glutamate

Abstract A novel rearrangement promoted by vitamin B12s of diethyl 1-keto-2-bromomethyl-2-methylsuccinate 10 to diethyl 4-methyl-2-ketoglutarate 11 has been discovered. This can serve as a partial model for the coenzyme B12 dependent enzyme catalyzed interconversion of β-methylaspartate and glutamate. The Schiff base corresponding to 10 does not react with vitamin B12s , but it does rearrange readily under free radical conditions when treated with tri-n-butyltin hydride.

A revision of the structure of the isoquinolone alkaloid thalflavine

Abstract The structure of the isoquinolone alkaloid thalflavine, originally proposed as 1-oxo-2-methyl-5-methoxy-6,7-methylenedioxy-1,2,3,4-tetrahydroisoquinoline, is revised to 1-oxo-2-methyl-5,6-methylenedioxy-7-methoxy-1,2,3,4-tetrahydroisoquinoline, on the basis of synthesis.

Mollinedine, a New Alkaloid from Mollinedia costaricensis.

~ S T ~ ~ . . \ ’ O l l i n e d i a C O J t a ~ C ~ l S is a plant indigenous to Central America, where it has been used as a medicinal. Chromatography of the alkaloidal fraction of an EtOH extract of the roots over Si gel afforded mollinedine, which was characterized as a new benzylisoquinoline alkaloid by a consideration of physicochemical and spectral data, as well as by conversion to escholamine and preparation from papaverine. Although mollinedine failed to exhibit any significant inhibitory activity against the in vitro growth ofa series ofstandard bacteria and fungi, preliminary pharmacological testing in rats and guinea pigs demonstrated an inhibitory effect against ouabain-induced and CaCI,-induced myocardial arrhythmias.

Dehydrodiscretine, an infrequently occurring quaternary protoberberine alkaloid from heptacyclum zenkeri

Abstract Dehydrodiscretine, a quaternary protoberberine alkaloid, has been isolated from Heptacyclum zenkeri Engl. (syn. Penianthus zenkeri Diels). This is the first reported isolation of this alkaloid from a member of the Menispermaceae and only the second reported isolation from nature.

Alkaloids of Thalictrum delavayi

Abstract The isolation and identification of six alkaloids from the whole plant of Thalictrum delavayi are described. The alkaloids isolated were the aporphines (+)-isocorydine, (+)-Ieucoxylonine, (+)-ocoteine, and (+)-magnoflorine; the bisbenzylisoquinoline alkaloid (+)-hernandezine; and the phenanthrene alkaloid thalicthuberine.