Glycosylidene Carbenes. Part 31

Abstract

Dedicated to Professor Jack D. Dunitz on the occasion of his 80th birthdayThe diastereoselectivity of the addition of NH 3 and MeNH 2 to glyconolactone oxime sulfonates and the structures of the resulting N-unsubstituted and N-methylated glycosylidene diaziridines wereThe 15 N-labelled glucono-and galactono-1,5-lactone oxime mesylates 1* and 9* add NH 3 mostly axially (> 3 : 1; Scheme 4), while the 15 N-labelled mannono-1,5-lactone oxime sulfonate 19* adds NH 3 mostly equatorially (9 : 1; Scheme 7). The 15 N-labelled mannono-1,4-lactone oxime sulfonate 30* adds NH 3 mostly from the exo side (> 4 :1; Scheme 9). The configuration of the N-methylated pyranosylidene diaziridines 17, 18, 28, and 29 suggests that MeNH 2 adds to 1, 9, 19, and 23 mostly to exclusively from the equatorial direction (> 7 : 3; Schemes 5 and 8). The mannono-1,4-lactone oxime sulfonate 30 adds MeNH 2 mostly from the exo side (85 : 15; Scheme 10), while the ribo analogue 37 adds MeNH 2 mostly from the endo side (4 : 1; Scheme 10). Analysis of the preferred and of the reactive conformers of the tetrahedral intermediates suggests that the addition of the amine to lactone oxime sulfonates is kinetically controlled. The diastereoselectivity of the diaziridine formation is rationalized as the result of the competing influences of intramolecular H-bonding during addition of the amines, steric interactions (addition of MeNH 2 ), and the kinetic anomeric effect.The diaziridines obtained from 2,3,5-tri-O-benzyl-d-ribono-and -d-arabinono-1,4-lactone oxime methanesulfonate (42 and 48; Scheme 11) decomposed readily to mixtures of 1,4-dihydro-1,2,4,5-tetrazines, pentono-1,4-lactones, and pentonamides.The N-unsubstituted gluco-and galactopyranosylidene diaziridines 2, 4, 6, 8, and 10 are mixtures of two trans-substituted isomers (S/R ca. 19 :1, Scheme 2). The main, (S,S)-configured isomers S are stabilised by a weak intramolecular H-bond from the pseudoaxial NH to ROÀC(2). The diaziridines 12, derived from GlcNAc, cannot form such a H-bond; the (R,R)-isomer dominates (R/S 85 : 15; Scheme 3). The 2,3-di-O-benzyld-mannopyranosylidene diaziridines 20 and 22 adopt a 4 C 1 conformation, which does not allow an intramolecular H-bond; they are nearly 1 : 1 mixtures of R and S diastereoisomers, whereas the O H 5 conformation of the 2,3:5,6-di-O-isopropylidene-d-mannopyranosylidene diaziridines 24 is compatible with a weak H-bond from the equatorial NH to OÀC(2); the (R,R)-isomer is favoured (R/S ! 7 : 3; Scheme 6). The mannofuranosylidene diaziridine 31 completely prefers the (R,R)-configuration (Scheme 9).

Glycosylidene Carbenes. Part 32

“…Sulfonylation of 1A/1B 95 : 5 with TsCl, naphthalene-2-sulfonyl chloride, and 2,4,6-triisopropylbenzenesulfonyl chloride gave 81% of 2E [19], 83% of 2F, and 64% of 2G, respectively. Similarly, the d-galacto diaziridines 3A/ 3B 95 : 5 and of the d-manno analogues 5A/5B 55 : 45 [2] yielded 4B and 6 in 63 and 55%, respectively.…”

“…[31] [32]), and for C(3) and C(6) of the 1,4-dihydro-1,2,4,5-tetrazine nucleus of 10 (149.7 ppm; cf. [2] [33 ± 35]). The NH signal of 10 is hidden by the signals of the Ph groups.…”

“…C(1) of 17A ± 17D resonates as d at 75.00 ppm ( 2 J( 15 N,H) % 5 Hz). Assuming that only 19B, 22A/22B, 25A/25B, and 28A/28B is attacked by TsCl 8 ), irrespective of the configuration at C(4) or at C (2).…”

“…Acetylation and Sulfonylation of Furanosylidene-Diaziridines. Acetylation of the mannofuranosylidene-diaziridine 30 [2] with Ac 2 O gave 63% of the N-acetylhydrazone 31A and 8% of the 1,2,4,5-tetrazine 32 (Scheme 5). Sulfonylation of 30 led to a similar result, namely to 61% of the N-tosylhydrazone 31B and 11% of 32.…”

“…The tetrazine 32 is probably formed by oxidation of the expected 1,4-dihydro-1,2,4,5-tetrazine. Tosylation of the N-methylated ribofuranosylidene-diaziridines 33A/33B/33C/33D 76 : 4 : 12 : 8 [2] with TsCl and chromatographic separation of the products yielded 44% of a 2 : 1 (E)/ (Z)-mixture of the N-methyl-N-tosylhydrazone 34 and 30% of the ribonolactone 35 Helvetica Chimica Acta ± Vol. 86 (2003) 2498 value of C(1) (149.5 ± 153.5 ppm; Table 3 in Exper.…”