Balawant S. Joshi

Structure of parthenolide

Abstract New degradation experiments and NMR data on the sesquiterpene lactone isolated from the roots of Michelia champaca and identified as parthenolide have led to revision of the structure I originally proposed by Sorm et al. to that depicted by IV.

The structure and synthesis of pimprinine

Abstract The mould metabolite pimprinine obtained from Streptomyces pimprina has been shown by degradation and synthesis to be 5,3′-indoyl-2-methyloxazole (III).

On the structures of girinimbine, mahanimbine, isomahanimbine, koenimbidine and murrayacine.

Abstract The isolation of mahanimbine, girinimbine and two new carbazole alkaloids isomahanimbine and koenimbidine from the leaves and roots of Murraya koenigii Spreng. is reported. Spectroscopic and degradative evidence has been presented supporting structures for girinimbine ( 3 ), mahanimbine ( 4 ), isomahanimbine ( 13 ), koenimbidine ( 17 ) and murrayacine ( 12 ).

Reversal of absolute stereochemistry of the pyrrolo[2,1-b]quinazoline alkaloids vasicine, vasicinone, vasicinol and vasicinolone

Abstract The previously assigned 3 R configuration of (−)-vasicinone has been reversed and this pyrrolo[2,1-b]quinazoline-9-one has been shown to have the 3 S -configuration ( 3 ) on the basis of an X-ray diffraction study of (+)-vasicinone hydrobromide. Likewise, the 3 R stereochemistry assigned earlier to (−)-vasicine (peganine) ( 1 ) on the basis of an X-ray analysis of its hydrochloride has also been reversed by reinvestigation of the X-ray diffraction analysis of the hydrobromide. The absolute stereochemistry of the alkaloids (+)-vasicinol ( 2 ) and vasicinolone ( 5 ) which have been inter-related, should also have the 3 S -configuration. A study of the 1 H nmr spectroscopy of (−)-vasicine by the use of Moshers method using MTPA [α-methoxy-α-(trifluoromethyl)phenylacetic acid] esters indicated an exception to this model for establishing the absolute configuration.

The crystal structure of 3-epicaryoptin and the reversal of the currently accepted absolute configuration of clerodin

Evidence, based on an X-ray assignmet of the chirality of 3-epicaryopti and a fresh X-ray study of clerodin bromolactone, is presented for the reversal of the long-held absolute configuration of clerodin, and new terminology is suggested to avoid confusion in future.

Some b-Carboline Alkaloids of Ailanthus malabarica DC

From the bark and roots of Ailanthus malabarica DC. we have isolated and characterised eight β-carboline alkaloids of which four are new. Their structures are elucidated by spectroscopic studies.

Structure and synthesis of heptaphylline

Abstract A carbazole alkaloid C 18 H 17 NO 2 designated heptaphylline has been isolated from the roots of Clausena heptaphylla Wt. & Arn. On the basis of spectral and chemical evidence it has been constituted as (III). This structure has been confirmed by its unambiguous synthesis. Girinimbine (IX) has also been isolated from this plant.

Synthesis of clausenin, xanthoxyletin, alloxanthoxyletin, xanthyletin and nor-dalbergin☆

Abstract The synthesis of clausenin is reported. Clausenin on methylation, NaBH4 reduction and dehydration of the secondary alcohol gives xanthoxyletin. The angular isomer of clausenin by a similar series of reactions gives alloxanthoxyletin. A convenient synthesis of xanthyletin and nor-dalbergin has also been achieved.

Isolation and structure of surangin A and surangin B, two new coumarins from Mammea longifolia (wight) Planch and Triana

From the roots of Mammea longifolia (wight) Planch and Triana two new 4-alkylated coumarins designated as surangin A and surangin B have been isolated. They have been constituted as II and III, on the basis of evidence largely resting on a combination of UV, IR, NMR and mass spectral data.

Alternative medicine: Herbal drugs nd their critical appraisal - Part I

Among alternative therapeutic approaches that have shown global popularity during the past decades, herbal medicine stands out as a major concern in the countries where allopathic medicine prevails. The sales of herbal products as health care adjuvants in these countries have increased exponentially. Lack of quality control, commercial profiteering and exploitation leading to adulterations, lack of proper knowledge about the herbs and their contents that may exhibit drug-drug interactions and other adverse side-effects, and inappropriate usage of the herbal products have become a cause for concern in the health care professions, particularly in the United States. This review provides an incisive description of the known chemical, pharmacological, clinical and toxicological profiles of four of the most widely used herbal products.