22.4 GLYCOSIDE FORMATION When a small amount of gaseous hydrogen chloride is passed into a solution of D-(+)-glucose in methanol, the reaction as follows CHO H OH H2C Ho--H HO CH3OH H OH CHOH HCI H OH CH2OH D-(+)-Glucose OH H2C HC HO HO HO HO OCH3 OH OCH methyl a-D-Glucopyranose methyl p-D-glucopyranose (甲基α-D-(+}吡喃(型)葡萄糖) (甲基β-D(+}-吡喃(型)葡萄糖) (mp,165℃ab25=+158 (mp,107℃[ab25=-33
22.4 GLYCOSIDE FORMATION When a small amount of gaseous hydrogen chloride is passed into a solution of D-(+)-glucose in methanol, the reaction as follows: CHOH O HO H2C OH HO OH D-(+)-Glucose O HO H2 C OH HO OH OCH3 CHO H OH HO H H OH H OH CH2OH methyl β-D-Glucopyranose (甲基 β-D-(+)-吡喃(型)葡萄糖) (mp, 107℃ [a]D 25 = -33 0 ) CH3OH HCl O HO H2 C OH HO OH OCH3 methyl α-D-Glucopyranose (甲基 α-D-(+)-吡喃(型)葡萄糖) (mp, 165℃ [a]D 25 = +158 0 ) +
The mechanism for the formation of the methyl glucosides OH OH HC H2C H2O HO HO OH H,C methyl OH OHCH2+H+ β-D- Gluco HC H pyranoside + hoch OH OH H+ methyl a -D-Gluco HO pyranose side
The mechanism for the formation of the methyl glucosides: O HO H2C OH HO OH OH O HO H2C OH HO OH OHCH3 + + H + - H + O HO H2C OH HO OH OH2 - H2O +H2O O HO H2C OH HO OH + + HOCH3 O HO H2C OH HO OH OHCH3 + + + H + - H + + H + - H + methyl α-D-Glucopyranoside methyl β-D-Glucopyranoside
Carbohydrate acetals, generally, are called glycosides. Foe example acetal of glucose glucoside acetals of mannose mannosides ketals of fructose- fructoside In acidic solutions, however, glycosides undergo hydrolysis to produce a sugar and alcohol OH OH H2C H2C HO HO HO NOCH3 H2O. H3O HO + R-Oh n OH OH OH Glycoside S ugal glycone (配醣) (醣) (糖苷配基)
acetal of glucose acetals of mannose ketals of fructose glucoside mannosides fructosides Carbohydrate acetals, generally, are called glycosides. Foe example: In acidic solutions, however, glycosides undergo hydrolysis to produce a sugar and alcohol: O HO H2C OH HO OH OCH3 O HO H2C OH HO OH OH H2O, H3O + + R-OH Glycoside (配醣) Sugar (醣) Aglycone (糖苷配基)
22.5 REACTIONS OF MONOSACCHARIDES Dissolving monosaccharides in aqueous base causes them to undergo a series of keto-enol tauomerizations that lead to isomerizastions O H—C H—C H一C-OH C-OH HO-C-H HO-C一H HO-C-H HO-C-H Ho-C-H H-C-OH H2O H- H—C-OH H—C-OH H—C-OH H—C-OH H—C-OH H—C-OH CH,OH CHOH CH,OH CH,OH OH-1 H20 CHOH OH C=0 H一C tautomerization HO-C-H -OH H—C-OH HO H H—C-OH H一C-OH CH,OH H—C-OH CH,OH
22.5 REACTIONS OF MONOSACCHARIDES Dissolving monosaccharides in aqueous base causes them to undergo a series of keto-enol tauomerizations that lead to isomerizastions. C H C OH C C HO H C H OH H OH CH2OH O H C C OH C C HO H C H OH H OH CH2OH O H C C OH C C HO H C H OH H OH CH2OH O H C HO C H C C HO H C H OH H OH CH2OH O H H2O H2O OH - OHC C OH C C HO H C H OH H OH CH2OH OH H H2O OH - tautomerization CH2OH C O C C HO H C H OH H OH CH2OH
22 5A FORMATION OF ETHERS A methyl glucoside can be converted to the derivative by treating it with excess dimethyl sulfate in aqueous sodium hydroxide HOH,C HOH,C -OH CH3- OSO3 CH3 HO HO C OCH Methyl glucoside (甲基配糖物) OC HOH,C repeated CO AOCH noch methylations OCH3 OCH3 Pentamethyl derivative (五甲基衍生物)
22.5A FORMATION OF ETHERS A methyl glucoside can be converted to the derivative by treating it with excess dimethyl sulfate in aqueous sodium hydroxide. O HO HOH2C HO OH OCH3 O HO HOH2 C HO O- OCH3 O HO HOH2 C HO OCH3 OCH3 O H3 CO H2 C OCH3 H3 CO OCH3 OCH3 -OH CH3 __ OSO3CH3 repeated methylations Methyl glucoside (甲基.配糖物) Pentamethyl derivative (五甲基衍生物）