Mechanisms of alkaline hydrolysis of p-nitrophenyl glucopyranosides

Abstract

Reaction of 15 (0.2 g in 1 ml of DMSO-de) with 1 equiv of potassium ieri-butoxide was observed directly by nmr. The AB pattern of the benzylic protons disappeared rapidly but there was no significant change in the chemical shift of the vinylic, SCH3, or OCHg resonances of 15. Attempts to isolate the product(s) of this reaction led only to the isolation of a sticky red solid which could not be recrystallized. Reaction of 15 with sodium hydride in dry THF in an inert atmosphere led to the immediate evolution of hydrogen, precipitation of NaBF4, and formation of a dark red solution which, after evaporating at reduced pressure, gave a red oil which solidified on washing repeatedly with pentane. Analysis by tic showed the presence of at least three components. Separation was unsuccessful, and the nmr of the crude product in CDC13 gave very broad signals which were uninformative as to structure.S-Benzyl-S-methyl-S-phenacylsulfonium ylide ( 14) was prepared from the corresponding sulfonium bromide salt by treatment with sodium hydride in THF.84 The sulfonium bromide was prepared from benzyl methyl sulfide and phenacyl bromide in benzene.Preparation of Sulfonium Salts 20.-Each of the salts was prepared from the corresponding sulfide by methylation with trimethyloxonium fluoroborate, as described above for 10. The salts so obtained were recrystallized to analytical purity from absolute ethanol. The sulfides were in turn prepared by the reaction of the appropriate thiophenol under basic conditions (sodium ethoxide in ethanol) with the appropriate phenacyl (24) K. W.

Selective electrochemical glycosylation by reactivity tuning1

“…The residue was purified by flash column chromatography to afford tetra-acetate 8 (28.2 g, 81%) as a white crystalline solid, m.p. 114-117 °C (ethyl acetate/petrol) (lit., 22 118 °C); [] 24 D −18 (c, 1.0 in CHCl 3 ) {lit., 22 [] 20 D −21 (c, 2.0 in CHCl 3 )};  H (400 MHz, CDCl 3 ) 1.99, 2.02, 2.09, 2.10 (4 × 3H, 4 × s, 4 × COCH 3 ), 2.36 (3H, s, PhCH 3 ), 3.70 (1H, ddd, J 4,5 10.1 Hz, J 5,6 2.6 Hz, J 5,6′ 4.8 Hz, H-5), 4.18 (1H, dd, J 6,6′ 12.3 Hz, H-6), 4.22 (1H, dd, H-6′), 4.64 (1H, d, J 1,2 10.1 Hz, H-1), 4.94 (1H, at, J 9.7 Hz, H-2), 5.03 (1H, at, J 9.9 Hz, H-4), 5.21 (1H, at, J 9.5 Hz, H-3), 7.13 (2H, d, J 8.1 Hz, ArH), 7.39 (2H, d, J 8.1 Hz, ArH).…”

“…The reaction mixture was concentrated in vacuo (co-evaporation with toluene) and the residue taken up in dichloromethane (200 ml), washed with sodium hydrogen carbonate (200 ml of a saturated aqueous solution), brine (200 ml), dried (MgSO 4 ) and concentrated in vacuo to afford alcohol 2 (1.26 g, 92%) as a white crystalline solid, m.p. 97-98 °C (ethyl acetate/petrol); [] 24 D +6.5 (c, 1.0 in CHCl 3 );  max (KBr disk)/cm −1 3500, 3084, 3061, 3027, 2960, 2917, 2872;  H (400 MHz, CDCl 3 ) 1.98 (1H, at, J 6.6 Hz, OH), 3.39 (1H, ddd, J 4,5 9.8 Hz, J 5,6 5.0 Hz, J 6,6′ 10.1 Hz, H-6), 3.37-3.50 (1H, m, H-5), 3.62 (1H, at, J 9.1 Hz, H-2), 3.67 (1H, dd, J 5,6′ 2.7 Hz, H-5), 3.48 (1H, dd, J 1,2 8.8 Hz, J 2,3 9.5 Hz, H-2), 3.56 (1H, at, J 9.4 Hz, H-4), 3.61-3.74 (1H, m, H-6), 3.74 (1H, at, J 9.1 Hz, H-3), 3.90 (1H, ddd, J…”

“…The reaction mixture was diluted with dichloromethane (200 ml), washed with water (100 ml), brine (150 ml), dried (MgSO 4 ) and concentrated in vacuo to afford phenyl glycoside 13 (8.4 g, 89%) as a white crystalline solid, m.p. 169-171 °C (ethyl acetate/petrol) (lit., 23 172-174 °C); [] 24 D +81 (c, 1.0 in CHCl 3 ) {lit., 23 [] 20 D +84.0 (c, 1.0 in CHCl 3 )};  H (400 MHz, CDCl 3 ) 4.51 (1H, dd, J 5,6 6.1 Hz, J 6,6′ 12.4 Hz, H-6), 4.59 (1H, dd, J 5,6′ 2.6 Hz, H-6′), 4.65 (1H, ddd, J 4,5 10.2 Hz, H-5), 5.54 (1H, dd, J 1,2 3.7 Hz, J 2,3 10.2 Hz, H-2), 5.80 (1H, at, J 9.9 Hz, H-4), 6.05 (1H, d, H-1), 6.46 (1H, at, J 9.8 Hz, H-3), 6.86-7.60 (18H, m, ArH), 7.93-8.04 (7H, m, ArH).…”

“…Ion exchange resin (Dowex 50) was added portionwise until the solution was neutralised, at which point the reaction mixture was filtered and concentrated in vacuo to afford tetrol 14 (2.8 g, 90%) as a white crystalline solid, m.p. 152 °C (ethanol) (lit., 24 160-161 °C); [] 22 D +84 (c, 1.5 in MeOH) {lit., 24 [] 21 D +179 (c, 1.25 in H 2 O)};  H (400 MHz, CDCl 3 ) 3.45 (1H, at, J 9.9 Hz, H-4), 3.58 (1H, dd, J 1,2 3.7 Hz, J 2,3 9.8 Hz, H-2), 3.66-3.77 (3H, m, H-5, H-6, H-6′), 3.88 (1H, at, J 9.4 Hz, H-3), 4.49 (1H, d, H-1), 7.01 (1H, at, J 7.4 Hz, ArH), 7.17 (2H, d, J 7.7 Hz, ArH), 7.29 (2H, at, J 8.0 Hz, ArH).…”

Interaction and reaction of the hydroxyl ion with β-d-galactose and its hydrated complex: an ab initio molecular dynamics study

“…It is well known that bases can accelerate the Maillard reaction, 1 an important chemical reaction between an amino acid and a reducing sugar. Under basic conditions, degradation of glycosides can occur, [2][3][4][5][6][7][8][9][10] which is one of the key steps in the synthesis of various glycosides and polysaccharides. In addition, degradation of cellulose, glucomannan and xylan, which are major wood components, 3,11 under basic conditions, is industrially very important.…”