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  • Author: Abdul Malik x
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Abstract

Recurvosides A (1) and B (2), new steroidal glucosides, have been isolated from the ethyl acetate soluble fraction of Haloxylon recurvum and their structures elucidated by spectroscopic techniques including two-dimensional NMR. Both the compounds exhibited potent antifungal activity.

The new secoiridoids Enicostemins A (1) and B (2) were isolated from the n-butanol-soluble fraction of Enicostemma verticillatum along with gentiocrucine (3) and rutin (4), which were isolated for the first time from the genus Verticillatum. Their structures were assigned based on spectroscopic studies.

Sparsifol (1), a new stereoisomer of inositol, and proaporphine alkaloid crotsparsidine (2), have been isolated from the EtOH extract of Croton sparsiflorus. Their structures were determined on the basis of 1H and 13C NMR spectra, DEPT, COSY, NOESY, HMBC, HMQC, EI-MS, and FAB-MS experiments

Thermal rearrangement of harmine hydroiodide (1) at 300 °C provided a new anhydronium base provisionally named as methylharmol (3). The structure was assigned on the basis of UV, IR and NMR spectral data of the base and its tetrahydro product (2). Nitration of methylharmol afforded 12-nitromethylharmol (4).

Abstract

Displacement of triflyl group by fluoride ion in benzyl 2,3-anhydro sugars leads with stereochemical inversion to fluorodeoxy sugars, providing a general method for the introduction of fluorine in the neighbourhood of oxirane ring in anhydro sugars. This procedure is mild, convenient, and does not experience difficulties which sometime are encountered in nucleophilic fluoride displacements in carbohydrate systems.

Abstract

A new approach for the synthesis of some sugar nitrates is described. The reaction sequence consists of esterifying partially protected carbohydrates with trifluoromethanesulfonic anhydride and reacting the resulting triflates with tetrabutylammonium nitrate. This procedure is mild, convenient and has the advantage of protecting highly acid-labile groups.

Displacement of the triflyl by the amino group in benzyl-2,3-anhydro-4-triflyl-pyranosides 4-6 gives with inversion the benzyl-2,3-anhydro-4-amino-4-desoxypyranosides 7-9. The triflyl group turns out to be a reactive leaving group which can be replaced by ammonia under mild conditions.

A new weak base from reserpine family has been isolated from Rauwolfia vomitoria Afzuelia and provisionally named as neonorreserpine. The chemical and spectral evidence established it as a distinct isomer of pseudoreserpine

Extensions of von Braun Cyanogen bromide reaction on Ephedra alkaloids and simpler bases have resulted in synthesis of substituted oxazolidines and a whole series of nitrogen analogues of ephedrine, desoxy ephedrine and simpler amines. The general applicability and limitations of such extension of the reaction are also discussed.

A convenient synthesis of the naturally occurring deoxyamino sugar forosamine from glucose as starting material is described. The yields for the intermediates (ethyl-4,6-di-O-toxyl-2,3-dideoxy-α-D-erythro-hex-2-enopyranoside, 4-iodo-2,3,4-tride-oxy-6-O-tosyl-α-D-threo-hex-2-enopyranoside, ethyl 4-azido-2,3,4-trideoxy-6-O-tosyl-α-D-erythro hex-2-enopyranoside, ethyl 4-amino-2,3,4,6-tetradeoxy-α-D-erythro-hexopyranoside) are all in the range between 70 to 80%.