Ove Kjølberg

Synthesis of acetylenic sugars and uronic acids via two-carbon chain extension of d-ribose

Abstract Treatment of methyl β- d -ribofuranoside with acetone gave methyl 2,3- O -isopropylidene-β- d -ribofuranoside ( 1 , 90%), whereas methyl α- d -ribofuranoside gave a mixture (30%) of 1 and methyl 2,3- O -isopropylidene-α- d -ribofuranoside ( 1a ). On oxidation, 1 gave methyl 2,3- O -isopropylidene-β- d - ribo -pentodialdo-1,4-furanoside ( 2 ), whereas no similar product was obtained on oxidation of 1a . Ethynylmagnesium bromide reacted with 2 in dry tetrahydrofuran to give a 1:1 mixture (95%) of methyl 6,7-dideoxy-2,3- O -isopropylidene-β- d - allo - ( 3 ) and -α- l - talo -hept-6-ynofuranoside ( 4 ). Ozonolysis of 3 and 4 in dichloromethane gave the corresponding d - allo - and l - talo -uronic acids, characterized as their methyl esters ( 5 and 6 ) and 5- O -formyl methyl esters ( 5a and 6a ). Ozonolysis in methanol gave a mixture of the free uronic acid and the methyl ester, and only a small proportion of the 5- O -formyl methyl ester. Malonic acid reacted with 2 to give methyl 5,6-dideoxy-2,3- O -isopropylidene-β- d - ribo - trans -hept-5-enofuranosiduronic acid ( 7 ).