Hexoses, complete synthesis

Fischer and Tafel s Complete Synthesis of Hexose Sugars a-ACROSE (from formaldehyde, glyceraldehyde, or acrolein dibromide) c H6NHNH2... 

The first synthesis of enantiomerically pure 1 was completed in 1980 by Tatsuta (Scheme 2.2). D-Glucose was converted via previously published procedures to the protected hexose 9. Benzylation of the hydroxy groups and cleavage of the thioacetal then gave intermediate 10 in 80% yield. This fragment will later be annealed onto a carbon chain and become C-1 to C-6 of the natural product. 

There has been a continuing interest in syntheses of 3-amino-2,3,6-trideoxy-hexoses such as daunosamine (9), acosamine (10), etc. In an interesting paper by Fronza et the two sugars have been synthesized from the non-carbohydrate compound (11), which was obtained in 25-30% yield from the incubation of cinnamaldehyde v th acetaldehyde in the presence of bakers yeast (Scheme 2). The crucial amino-lactone (12) was also synthesized from L-threonine. The same authors have also completed their synthesis of A-benzoyl-L-ristosamine (3-benzamido-2,3,6-trideoxy-L /6o-hexose) from 3-benzamido-2,3,6-trideoxy-L-xy/o-hexono-1,5-lactone (Vol. 13, p. 79). An alternative synthesis of methyl A-acetyl-a-L-acosaminide (13) has been described by reduction of the appropriate acetylated oxime by diborane. The thioglycoside (14) was also prepared. ... 

All the enzymes of the hexose monophosphate shunt have been found in the supernatant fraction of the cell. The enzymes of the glucuronic pathway, with the exception of NADP-L-hexonate dehydrogenase and aldonolactonase, which are found in the supernatant fraction of the cell, have a complex intracellular distribution. All the enzymes involved in glucuronic acid-1-phosphate synthesis and in the conversion of glucuronic phosphate or glucuronic acid to L-xylose or ascorbic acid are associated with the endoplasmic reticulum. The enzymes involved in the conversion of L-xylose to D-xylose are found in mitochondria. Thus, the complete glucuronic pathway involves three different cell fractions. 

With the synthesis of gulose, one of the two remaining hexoses (the products of chain lengthening of o-xylose) was identified as structure 9. By process of elimination, the other, D-idose, could be assigned structure 10, thus completing the exercise. 

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