Ishwaranes

Photo-addition of allene to the enone (90) yield adduct (91) in 75 % yield, which was subjected to ketalization in 77% yield. Epoxidation of (92) with perbenzoic acid followed by chromatography on alumina afforded two expoxides (93) and (94). Both (93) and (94) could be converted separately through (95) and (96) respectively which was the common intermediate leading to isoishwarane (98) and ishwarane following a deketalization-retroaldol-aldol process to furnish the keto-alcohol (97) (99) 30>. 

Ishwarane (371) has been isolated from the petals of Cymbopetalum penduli-forum (Dunal) Baill. Last year, Kelly et al. reported the synthesis of isoish-warane (372) which they have now extendedto the synthesis of ishwarane itself. The enone (373) was converted in five steps into the ketol (374). Treatment of the tosylate of (374) with dimsyl sodium afforded the cyclized ketone (375) which gave ishwarane on Wolff-Kishner reduction. The complete details of the elegant synthesis of hinesol (376) by Marshall and Bradyhave now been published. 

In addition to ( )-valerane, a wide variety of other sesquiterpenes, including ( )-ishwarane, ( )-ish-warone, ° copaene, ylangene, ( )-seychellene ( )-sativene, ( )-longifoline, " ( )-copa-camphene," ( )-damsin," ( )-A < >-capnellene, ( )-pentalenene, (-)-P-vetivone" and ( )-P-eudesmol have been synthesized by pathways involving cycloalkylation of saturated ketone enolates. 

A new type of. seco-ishwarane alcohol (724) has been identified in the roots of Aristolochia indica.326 This compound, which co-occurs with (+)-ledol (725), has antifertility properties when tested on mice. Its structure was deduced on the basis of spectral analysis together with its correlation with a derivative of ishwarane (726). A full report on the synthesis of ishwarone (727) has been presented.327... 

The isolation and structural elucidation of the novel tetracyclic sesquiterpenes ishwarane (311, R = and ishwarone (311, R = O), obtained from the... 

An alternative shorter synthetic route to ( )-ishwarane (512) cf. Vol. 8, p. 118) has been achieved by using a carbene insertion reaction to construct the tetracyclic framework (Scheme 49)/ The first synthesis of ( )-ishwarone (518),... 

Rao et al. isolated ishwarone (391) as one of the chief constituents of the roots of A. indica [347], Subsequent investigations by Ganguly et al. and Govindachari et al. led to the first structural assignment of ishwarone (391) as a novel tetracyclic sesquiterpene ketone based on eremophilane skeleton, the first of its kind to occur in the nature [348,349]. Ishwarane (388), reported from the roots of A. indica by Govindachari et al. is the first tetracyclic sesquiterpene hydrocarbon based on the eremophilane skeleton [334], A tetracyclic sesquiterpene alcohol, ishwarol (389) is also reported from the roots of A. indica [350]. Pakrashi et al. isolated (125)-... 

Ishwarane (20) and ishwarone (25) are two novel tetracyclic sesquiterpenes which have been isolated from Aristolochia indica Linn, and other tropical plants a synthesis of ishwarane was reported by Kelly and his co-workers in 1971. Kelly and Alward have now effected an improved synthesis of the hydrocarbon, which... 

Ishwaranes represent 7-11/10-12-bicycloeremophilanes. These rare tetracyclic sesquiterpenes are found in Aristolochiaceae, for example ishwarane itself and ish-waranol in the roots of Aristolochia indica and 3-ishwaranone from Aristolochia debilis. 

From the roots of Aristolochia indica, the tetracyclic sesquiterpenes ishwarane (252) and ishwarone (253) have been isolated (314). A few other related compounds are known. Biogenetically, they appear to be derived from the nootkatane cation (240). 

The coloring principles are carotenoids, mostly bixin (oil-soluble) and norbixin (water-soluble), with bixin (especially the cis isomer) in major concentration (2.5% dry wt.). Norbixin is the principle component of the water-soluble dyes of annatto and is formed by the removal of the methyl esters of bixin. Both a- and P-forms of norbixin are found in water-soluble annatto dye. (—)-Bixin (syn. a-bixin) is unstable and during extraction is usually converted to trans-hixin (syn. P-bixin), the stable isomer, which is also known as isobixin. Bixin is a monomethyl ester of norbixin (a dicarboxylic acid) it is readily hydrolyzed by alkalis during alkali extraction of annatto to the dicarboxylic acid, norbixin (evans MERCK).Annatto also contains P-carotene (6.8-11.3 mg/lOOg), apocarotenoids, diapo-carotenoids, an essential oil (with the sesquiterpene ishwarane as the major component), pentosans, pectin, protein (13-17%), tannins, and others (evans). 

The synthetic route to ishwarane, a novel tetracyclic sesquiterpene, proceeds through the bicyclic intermediate (A) bearing not only the C-4, C-5 c/s methyl groups, but also possessing an a, -unsaturated ketone functionality suitable for development of the tricyclooctane system. This has been accomplished by photo-addition of allene to (A), followed by skeletal rearrangement of the resulting cyclobutanol (B) into intermediates possessing a bicyclo[2-2-2] octane system (C) and, finally, the transformation of the bicyclooctane system into the desired tricyclo[3-2-10 > ] octane system. 

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