ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Ginkgolide B (1b) has been glucosylated in THF with the glucosylidene-derived diazirine 2 under thermal or photochemical conditions. Depending on the amount of 2, we obtained either monoglucosides (5-8), diglucosides (13-17), or triglucosides (21-23). In keeping with earlier results, the use of THF as solvent led mostly to β-D-glucosides. The modest regioselectivity in the formation of the monoglucosides, glucosylated either at O—C(1) or O—C(10), is rationalized on the basis of the relative kinetic acidity of the intra- and intermolecularly H-bonded OH groups of 1b. The tertiary HO—C(3) of the monoglucosides was more readily glucosylated than the secondary HO—C(1) or HO—C(10) (H-bonded). Glucosidation with 3.5 equiv. of 2 led to triglucosides, with the tri-β-D-glucoside 21 (42%) as the major product. Catalytic hydrogenation afforded the free glucosides 9-12, 18-20, and 24. The di- and triglucosides are readily soluble in H2O. Glucosidation with 2 of the ginkgolide-A-derived tertiary alcohol 25 yielded 93% of the β-D-anomeric glucoside 26. Similarly, glycosidation of 25 with the lactosylidene-derived diazirine 34 proceeded with a very high stereoselectivity, yielding 92% of the β-D-lactoside 35, that was deprotected to the H2O soluble acetate 36.
Additional Material:
2 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19970800808
Permalink
