Glycosylidene Carbenes. Part 18. Insertion of glycosylidene carbenes into the Sn?H bond of tributyl- and triphenylstannane: A synthesis of stannoglycosides |
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Authors: | Peter Uhlmann,Daniel Nanz,Eva Boz ,Andrea Vasella |
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Affiliation: | Peter Uhlmann,Daniel Nanz,Eva Bozó,Andrea Vasella |
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Abstract: | Insertion of the glycosylidene carbenes, derived from the gluco- and the manno-diazirines 1 and 2 , into the Sn? H bond of R3SnH (R = Bu or Ph) leads to the fully substituted stannoglycosides 3 – 8 (53–77%). The 1,2-cis-configurated products are formed preferentially (α-D /β -D ranges from 2.5:1 to 5.1:1 with 1 , and 1:1.3 to 1:4.2 with 2 ). Relative to CH2Cl2, THF favors formation of the equatorial Sn-glycosides. The stannylated (benzyloxy)glucals 9 and 10 were isolated as side products. The reaction of 1 with (Bu3Sn)2 yielded 9 (17% in CH2Cl2; 36% in CCl4) together with the azines 11 and the benzyloxyglucal 12 . NMR Data of the Sn-glycosides 3 – 8 show evidence for an anomeric effect, 1J(C(1),H) being larger in the axial and 1J(Sn,C(1)) larger in the equatorial anomers. |
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