The chemistry of dicarbonyl sugars. The base catalyzed cyclization of a -hepto-2,6-diulose to an unusual cyclohexenone

The conversion of carbohydrate derivatives into functionalized cyclohexanes and cyclopentanes

“…Intermediates 57-59 are thought to be involved in the cyclization process (Scheme 11). 35 It was then observed that compound 57 was the principal product initially formed when the dibromide 56 was treated with sodium acetate in acetone, but in this solvent (which could not participate in the reaction as did ethanol in giving 60) reaction continued by way of 61 and 62 to give the dienone 63 as product (Scheme 11) .36'37 Cyclization of bromide 56 to the diazido product 64 was effected by treatment with sodium azide.…”

.delta.-Dicarbonyl sugars. 5. A novel synthesis of a branched-chain cyclitol

“…

The cyclization of tri-0-acetyl-l,7-dideoxy-l,7-bis(diazo)-ryio-2,6-heptodiulose (5), in acetic acid solution, to 4,5,3,4, is described. This conversion, considered to take place by way of a carbene, represents a new synthesis of the cyclitol ring system.

…”

“…A minor product from the decomposition of 5 was identified as penta-Oacetyl-rylo-2,6-heptodiulose (9).The biosynthetic pathways that lead to the carbocyclic ring system as it is found in the cyclitols3 are thought to involve enzyme-catalyzed aldol condensations of appropriate -dicarbonyl monosaccharides. We have recently discovered that some synthetically prepared derivatives of this class of carbohydrates can be chemically induced to undergo these same ring closures.1•4 This paper describes a new route to the acetylated hydroxymethylcyclitol 3,4,5, by way of an unusual cyclization of a bisdiazo ketone (5) derived from xylo-2,6heptodiulose.…”

“…(4). Sodium bicarbonate (3 g, 0.035 mol) was slowly added to a solution of tri-O-acetyl xylaric an-h i b i t e d .…”