Albicanol

This was demonstrated by Fukumoto and co-workers in a synthesis of (+)-albicanol (251), a sesquiterpene with potent hsh antifeedant properties (272,273). Oxime 248 [prepared from the (+)-Wieland-Miescher ketone 247] was subjected to cycloaddition using sodium hypochlorite and gave isoxazoline 249 in very good yield (Scheme 6.95). Conversion of 249 into (3-hydroxyketone 250 was again accomplished by the reductive hydrolysis sequence using Raney Ni and trimethyl... 

In another study C. luteomarginata, collected from two locations (Howe Sound and Barkley Sound) in British Columbia (68), was found to contain albicanyl acetate [79], albicanol [80],... 

It is necessary to mention that authors [40] showed that the albicanol (43) isomerises into the drimenol (2) in high yields (93%) on treatment with boron trifluoride etherate. 

Earlier it was indicated (Schemes 5, 7, 10) that the hydroxy acetate (42) was transformed into the drimenol (2) [49], its acetate (12) [42] or a mixture of the drimenol (2) and the albicanol (43) [39]. Authors [55] accomplished the targeted synthesis of the albicanol (43) and its acetate (68) starting with the hydroxy acetate (42) (Scheme 12). The hydroxy acetate (42) was dehydrated with thionyl chloride into the mixture of acetates (12), (67) and (68), which was subjected to oxidation with m-CPBA. On that treatment the acetates (12) and (67) are selectively oxidised, but the acetate (68) remained unreacted. The latter was than isolated by chromatography and saponified into the albicanol (43). The overall yield of the albicanyl acetate (68) and the albicanol (43) was 61% (at the saponification step the yield of (43) was quantitative). Barrero et al. 

It should be mentioned that the albicanyl acetate (68) is a biologically active substance, being a powerful antifeedant for fish [56]. The albicanol... 

ABSTRACT The Wieland-Miescher ketone (1) and its methyl analog (2) have been utilized for the synthesis of several sesquiterpenes like warburganal, muzigadial, albicanol, etc. Similarly several bioactive diterpenes like taxodione, pisiferic acid, aphidicolin, etc., have been synthesized from these ketones. The utility of several reagents in the total synthesis of terpenoid compounds has been documented. The developments of several routes for a single terpene from these ketones have been discussed. 

Albicanol (66), a drimane-type sesquiterpene, was isolated from the liverworts Diplophyllum albicans [30] and also from the dorid nudbranch Cadlina luteomarginata [31] together with its acetate (67) which exhibits potent fish antifeedant activity. 

Fig. (6). A simple and enantioselective synthesis of (+)-albicanol (66) is desccribed. The hydroxy-ketone (60), prepared from the (-) Wieland-Miescher ketone, undergoes ring cleavage with lead tetra-acetate in methanol. The resulting product on ketalization leads the formation of the product (61) which is converted to oxime (63) by the standard reactions. Intramolecular cyclization followed by reductive hydrolysis and methylenation afforded (+)- albicanol (66).

Banerjee and co-workers [36] have also developed an alternative route for the synthesis of the racemic albicanol (66) as described in "Fig (7)". The starting material for the present synthesis was the alcohol (68) [37] prepared from the Wieland-Miescher ketone (1), which on dehydration afforded the olefin (69). This on allylic oxidation yielded the a,P unsaturated ketone (70) in 88% yield. It was converted to the keto ester... 

Fig. (7). A total synthesis of (+)-albicanol (66) is described. The alcohol (68), Obtained from the Wieland-Miescher Ketone was Converted to the Diol (73) by the Standard Organic Reactions. The Keto Alcohol (74), Obtained from the Diol (73) by Selective Oxidation, was Subjected to Tetrahydropyranylation, Wittig Reaction and Dehydropyranylation to Obtain Albicanol (66).

A simple drimane-type sesquiterpene alcohol, (—)-drimenol (297) which is the direct cyclization product of farnesol, has been isolated from Bazzania trilobata (149). Albicanol (298), a double bond isomer of (297), was isolated from Diplophyllum species its structure and stereochemistry were established on the basis of the LIS-values in H-NMR spectrum, the formation of the same drimanol, on hydrogenation of (297) and (298) and the observation that acid-catalyzed isomerization of (297) and (298) gave the same mixture of products (281). 

Further investigation of the extract of Japanese Bazzania species resulted in the isolation of two new albicanyl esters (299, 300) 334). The stereochemistry of albicanol (298), also prepared by hydrolysis of albicanyl 3,4-dimethoxycinnamate (308) was confirmed by examining the CD spectrum of a six-membered ketone (309) which showed a negative Cotton effect (307 nm, As, —1.20) (Scheme 35). 

Akita, H., Nozawa, M., Mitsuda, A., and Ohsawa, H. (2000) A convenient synthesis of (-l-)-albicanol based on enzymatic function total syntheses of (-l-)-albicanyl acetate, (-)-albicanyl 3,4-dihydroxycinnamate, (-)-drimenol, (-)-drimenin and (-)-ambrox. Tetrahedron Asymmetry, 11,1375-1388. 

Shishido, K, Tokunaga, Y, Omachi, N., Hiroya, K, and Fukumoto, K. (1990) Total synthesis of (+)-albicanol and (+)-albican acetate via a highly diastereoselective intramolecular [3+2] cydoaddition./. Chem. Soc. Perkin Trans. /, 2481—2486. 

Anilkumar, A.T., Sudhrr, U., Joly, S., and Narr, S.M. (2000) Studies in lipase catalyzed trans-esterifications synthesis of (+)-albicanol, (+)-albicanyl acetate and chiral intermediates useful in the synOiesis of drimanes and labdanes. Tetrahedron, 56,1899-1903. 

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