Two novel metabolites of mixed biogenesis, polycerasoidin [1] and polycerasoidol [2], have been isolated from the stem bark of Polyalthia cerasoides. Their structures were established on the basis of nmr spectroscopic techniques, including 2D correlated nmr spectroscopy (COSY 45, HMQC, and HMBC).The genus Polyalthia includes more than 150 species of trees belonging to the family Annonaceae. It is considered one
A new furanopyrone derivative, (−)-etharvensin (1),
was isolated from the stem bark of
Goniothalamus arvensis. Semisynthesis of the
7-ethoxyfuranopyrone 1 was achieved by
addition of EtOH in concentrated acid medium to the unsaturated
α-pyrone (+)-altholactone
(2). This protocol constitutes a novel, direct
(single-step), and efficient method to prepare this
class of bioactive compounds.
Optically pure (1S,R)- and (1R,S)-benzyltetrahydroisoquinolines (BTHIQs), 12a,b as the major diastereomers, were prepared by stereoselective reduction of the isoquinolinium salt possessing (R)- and (S)-phenylglycinol as the chiral auxiliary, respectively. The absolute configurations of (1S,R)-13a hydrochloride (O-debenzoylated derivative from 12a) and (1R,S)-12b diastereomers were unambiguously determined by single-crystal X-ray analysis. Reductive removal of the chiral auxiliary group, subsequent N-propylation, and cleavage of the methylenedioxy group furnished the optically active catecholamines (1S)-16a and (1R)-16b in good overall yield. We have separately prepared for the first time pairs of dopaminergic 1-BTHIQs enantiomers through a classical methodology in asymmetric synthesis. The (1S)-enantiomers (14a-16a) bind to D1 and D2 dopamine receptors with affinities 5-15 times higher than those of the corresponding (1R)-enantiomers (14b-16b). Moreover, (1S)-14a inhibits [3H]dopamine uptake with high affinity. It appears that synthesis and testing of (S)-enantiomers of BTHIQ are very important for the search for new active drugs at dopamine receptors.
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