Sedoheptulose and Sedoheptulosan

The equilibrium mixture obtained when either sedoheptulose or sedoheptulosan is heated with dilute acid was believed to contain 20% of the sugar and 80% of the anhydride. However, chromatographic examinations - showed a more complex mixture, and two additional components were isolated by use of thick-paper chromatography. One of these appeared to be 5-(l,2-dihydroxyethyl)-2-furaldehyde (72), a product... 

N. K. Richtmyer and J. W. Pratt, Sedoheptulose. Its rotation, reducing power, equilibrium with sedoheptulosan in acid solution, and crystalline hexaacetate also crystalline 2,7-anhydro-fS-D-altro-heptulofuranose, J. Am. Chem. Soc., 78 (1956) 4717-4721. 

Frontalin (29) 47), brevicomin (30) 48), and multistriatin (31) (72) pheromonal constituents of a number of beetles, all possess the dioxabi-cyclo (3.2.1) octyl skeleton (Scheme 8). These ring systems are frequently encountered in carbohydrate chemistry where they are known, most commonly, as 1,6-anhydro sugars 97) since they are formally obtained by cyclodehydration of hydroxyl groups at positions 1 and 6. Actually 1,6-anhydro-D-glucose or levoglucosan (32) is best prepared by pyrolysis of starch (97). However with sedoheptulose (33) dehydration occurs spontaneously giving sedoheptulosan (34). 

The action of an enzyme, transketolase, from rat liver or from spinach, on pentose 5-phosphate results in the formation of a triose phosphate and an ester of sedoheptulose, which is presumably sedoheptulose 7-phosphate. The heptulose has been identified by the preparation of sedoheptulosan tetrabenzoate (227). 

Recent work by Calvin and co-workers and by Horecker et al. have demonstrated the importance of sedoheptulose in the photosynthetic cycle of the carbohydrates as being a transitory intermediate in the regeneration of D-erythropentulose, the monosaccharide involved in the fixation of carbon dioxide . This sugar also plays a part in animal carbohydrate metabolism. Its most characteristic chemical property is its ready conversion into sedoheptulosan.(2,7-anhydro-j8-D-altroheptulopyranose (LVII). 

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