GLYCOSYLIDENE CARBENES .18. INSERTION OF GLYCOSYLIDENE CARBENES INTO THE SN-H BOND OF TRIBUTYLSTANNANE AND TRIPHENYLSTANNANE - A SYNTHESIS OF STANNOGLYCOSIDES

Insertion of the glycosylidene carbenes, derived from the gluco- and t he manno-diazirines 1 and 2, into the Sn-H bond of R(3)SnH (R = Bu or Ph) leads to the fully substituted stannoglycosides 3-8 (53-77%). The 1,2-cis-configurated products are formed preferentially (alpha-D/beta- D ranges from 2.5:1 to 5.1:1 with 1, and 1:1.3 to 1:4.2 with 2). Relat ive to CH2Cl2, THF favors formation of the equatorial Sn-glycosides. T he stannylated (benzyloxy)glucals 9 and 10 were isolated as side produ cts. The reaction of 1 with (Bu(3)Sn)(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, (1 )J(C(1),H) being larger in the axial and (1)J(Sn,C(1)) larger in the e quatorial anomers.