Insertion of the glycosylidene carbenes derived from the diazirines 1, 14, and 15 into the BÀalkyl bond of the B-alkyl-9-oxa-10-borabicyclo[3.3.2]decanes 5, 6, and 7 yielded the stable glycosylborinates 8/9 (55%, 55 : 45), 10/11 (31%, 65 : 35), 12/13 (47%, 60 : 40), 16/17 (55%, 55 : 45), 18/19 (47%, 45 : 55), and 20/21 (31%, 30 : 70). Crystal-structure analysis of 17 and NOEs of 9 and 19 show that 17, 9, and 19 adopt similar conformations. The glycosylborinates are stable under acidic, basic and thermal conditions. The unprotected glycosylborinate 25 was obtained in 80% by hydrogenolysis of 12. Insertion of the glycosylidene carbene derived from the diazirine 1 into a BÀC bond of BEt 3 , BBu 3 , and BPh 3 led to unstable glycosylboranes that were oxidised to yield the hemiacetals 29 (55%), 31 (45%), and 33 (48%), respectively, besides the glucals 30 (13%), 32 (20%), and 34 (20%), respectively. Insertion of the glycosylidene carbenes derived from 14 and 15 into a BÀC bond of BEt 3 led exclusively to hemiacetals; only 15 yielding traces of the glucal 40 besides the hemiacetal 39. The glycosylidene carbene derived from 1 reacted with Al( i Bu) 3 and AlMe 3 to generate reactive glycosylalanes that were hydrolysed, yielding the C-glycosides 46 (21%) and 49 (30%), respectively, besides the glucals 48 (26%) and 51 (30%); deuteriolysis instead of protonolysis led to the monodeuterio analogues of 46 and 49, respectively, which possess an equatorial 2 H-atom at the anomeric center.Introduction. ± Glycosylidene carbenes, generated by thermolysis or photolysis of diazirines, insert into XÀH bonds to form O-, C-, and N-glycosides [2 ± 6], glycosylphosphines [7], and glycosylstannanes [8].We considered that the nucleophilic attack 2 ) of glycosylidene carbenes (e.g., 2) on triligated B or Al derivatives should lead to tetraligated intermediates, such as the Bylide 3 (Scheme 1). These ylides are expected to undergo (axial or equatorial) migration of a B or Al substituent, respectively, as shown in Scheme 1 for glycosylboranes 4, by analogy to the known migration of a B substituent in tetraligated borates that possess a vicinal leaving group [12] [13]. They should lead to C(1)-substituted
