~~ ~Phenol, 4-methoxyphenol, 4-nitrophenol, methyl orsellinate (l), and 2,6-di(tert -butyl)-4-methylphenol (BHT; 2) have been glycosylated by thermal reaction (20-60") with various glycosylidene-derived diazirines.4-Methoxyphenol reacted with the D-glucosylidene-derived diazirine 3 to give 0-glucosides (4 and 5, 69 %, 3:l) and C-glucosides (6 and 7, 16%, 1:l). Similarly, phenol yielded 0-glucosides (10 and 11, 70%, 4:l) and C-glucosides (12 and 13, 13%, 1:l). 4-Nitrophenol gave only 0-glycosides, 3 leading to 14 and 15 (75%, 3:2; Scheme I ) , and the D-galactosylidene-derived diazirine 17 to 22 and 23 (52% (from 16), 65:35; Scheme 2). The reaction of phenol with 17 yielded 58% (from 16) of the 0-galactosides 18 and 19 (4:l) and 14% of the C-galactosides 20 and 21 (1 :I). From the D-mannosylidene-derived diazirine 25, we predominantly obtained the a -D-configurated 26 (38 % from 24). These results are interpreted by assuming that an intermediate (presumably a glycosylidene carbene) first deprotonates the phenol to generate an ion pair which combines to give 0-and -with electron-rich phenolates -also C-glycosides. A competition experiment of 3 with 4-nitro-and 4-methoxyphenol gave the products from the former (14 and 15) and the latter phenol ( k 7 ) in almost equal amounts. Differences in the kinetic acidity of OH groups, however, may form the basis of a regioselective glycosidation, as evidenced by the reaction of 3 with methyl orsellinate (1) yielding exclusively the 4-0-monoglycosylated products 27 and 28 (78%, 85: 15), although diglycosiddtion is possible (27+ 31 and 32; 67%, 4:3; Scheme 3 ) . Steric hindrance does not affect this type of glycosidation; 3 reacted with the hindered BHT (2) to afford 33 and 34 (81 %, 4:l). The predominant formation of 1,2-trans-configurated 0 -aryl glycosides is rationalized by a neighbouring-group participation of the 2-benzyloxy group.
