From sterile root cultures of Datura stramonium, an NADP(H)-specific tropine dehydrogenase has been isolated and characterized. The enzyme catalyzes the reversible and stereospecific oxidation of tropine and related tropane-3 alpha-ols to the corresponding ketone. Isomeric pseudotropine (tropane-3 beta-ol) is neither accepted as substrate nor produced in the reverse reaction. It is assumed that this dehydrogenase is involved in the biosynthesis of tropane alkaloids.

Tropoyl coenzyme A has been synthesized in good yields via the corresponding N-hydroxysuc-cinimide ester. The UV-spectrum of the purified thioester has an absorption maximum at 257 nm; at this wavelength, a molar extinction coefficient of 19.2 × 106 [cm2 mol-1] has been determined. Upon alkaline hydrolysis of the thioester bond a difference spectrum with Amax at 235 nm (Δe235= 4.8 × 106 [cm2 mol-1]) has been observed. Attempts to prepare 2-phenylmalonyl coenzyme A by the same technique gave negative results.

a-Formylphenylacetic Acid, Phenylmalonic Semialdehyde, Tropic Acid Biosynthesis a-Formylphenylacetic acid, the postulated immediate precursor of tropic acid, has been synthesized by deacetalization of a-diethoxymethylphenylacetic acid in the presence of silica gel. The compound was reasonably stable in organic solution. In aqueous media, however, a pronounced lability of this semialdehyde was observed at various pH-values (t/2 = 4.5 min at pH 7.4). It is thus very unlikely that this compound can be employed successfully in biosynthetic studies.