Sorbitol 2.3- 0- isopropylidene

The 5,6-anhydro derivatives of D-sorbitol and D-mannitol41 69 behave in like manner to the 5,6-anhydro-l,2-isopropylidene-D-glucofuranose of Freudenberg and coworkers.70 Thus, 5,6-anhydro-l,3 2,4-diethyli-dene-D-sorbitol (LXXXV) readily suffers ring scission with ammonia to give 6-amino 6-desoxy-l,3 2,4-diethylidene-D-sorbitol (LXXXVI)69 or with sodium methoxide to form 6-methyl-l,3 2,4-diethylidene-D-sorbitol.42 l,2 3,4-Diisopropylidene-5,6-anhydro-D-mannitol gives rise... 

Isosorbide and isomannide are important by-products of the starch industry, arising from dehydration of D-sorbitol and D-mannitol. These commercial starting materials provide an easy and inexpensive access to optically pure functionalized tetrahydrofurans like 04,05-isopropylidene-1-iodo-3,6-anhydro-1-deoxy-D-glucitol and 04,05-isopropylidene-l-iodo-3,6-anhydro-1-deoxy-Q-mannitol. This procedure describes a preparation of the former compound and the epoxide derived therefrom. 

D-Glucose was reduced to the D-sorbitol with a hydrogen over Ni Raney, then it was turned into the L-sorbose with the acetobacter suboxydans and the hydroxyl groups of L-sorbose were protected with acetone treatment yielded the diaceton-L-sorbose. Subsequent treatment with NaOCI/Raney Ni produced di-O-isopropylidene-2-oxo-L-gulonic acid. Partial hydrolysis with aqueous HCI gave deprotected 2-oxo-L-gulonic acid, which yielded ascorbinic acid by heating with HCI. 

Iodo-desoxy derivatives of methylene, benzylidene and isopropylidene compounds have been transformed into their desoxy analogues with Raney nickel and hydrogen in basic media (e.g. hydroxides, methoxides and diethylamine). 0 47,60,81,82 Under similar conditions, l,3 2,4-diben-zylidene-5,6-sorbitoleen has been hydrogenated 8 and 2,4-benzylidene-6-nitro-6-desoxy-D-sorbitol has been converted into the corresponding amine.84 We are not aware of any report in this field of the removal of a benzylidene group by Raney nickel, as is the case with certain sugar derivatives.88... 

The monoacetone compound consumed three molecular equivalents of periodate, thus limiting the location of the ketal group to the 1,2- or 5,6-positions (see page 147, 1,6- improbable).148 The major fragment which resulted from its oxidation with lead tetraacetate was isopropyli-dene-L-glyceraldehyde, identified by conversion into L-glyceraldehyde 2,4-dinitrophenylhydrazone. This eliminated the 5,6-structure and clearly defined the parent compound as 1,2-isopropylidene-D-sorbitol.143... 

The diacetone compound was shown to be l,2 5,6-diisopropylidene-D-sorbitol by the fact that it consumed one mole of periodate with the concomitant formation of isopropylidene-D,L-glyceraldehyde, but not of formaldehyde (see page 147).148... 

The acetonation of 2,4-benzylidene-D-sorbitol has been studied by Vargha135 and by Laan and Dekker 88 when copper sulfate is employed as the catalyst a mono- and a di-isopropylidene derivative (m. p. 179° and 131°, respectively) are obtained. An interesting point about the latter compound is that, unless acetal rearrangement occurs during the acetonation stage, it must contain at least one isopropylidene group which is not united to adjacent positions in the hexitol molecule. 

In the modern industrial manufacturing proce.ss, the reduction to d-sorbitol is accomplished either electrolytically or by catalytic hydrogenation (Ha/CuCrOa). Additionally, it has been found that the reaction of sorbose with acidified acetone at low temperature (— 5 °C) gives a greatly increased yield of the di-O-isopropylidenyl (as opposed to the 2,3-mono-O-isopropylidenyl) derivative. The oxidation of this protected sorbose (2,3 4,6-di-0-isopropylidene-L-sorbofuranose or diacetone sorbose ) to the corresponding 2,3 4,6-di-0-isopropylidene-2-... 

Industrial-scale production of ascorbic acid also starts with glucose. The sugar is first reduced to sorbitol (VI) and then oxidized with Acetobac-ter suboxidans to L-sorbose (VII) which after cyclization and conversion to the diisopropylidene derivative (VIII) is oxidized to the corresponding derivative of L-2-oxogulonic acid (IX). After removal of the protecting isopropylidene groups, L-ascorbic acid (vitamin C) is obtained via L-2-oxogulonic acid (X cf. Reaction 18.41). 

Figure 2.20 Structures of sugar diols (a) D-isosorbide, (b) isomannide, (c) methyl 4,6-0-benzylidene-a-D-glucop5Tanoside, (d) methyl 2,6-di-O-pivaloyl-a-D-glucopyranoside, (e) l,2 5,6-di-0-isopropylidene-D-sorbitol, and (0 2,3,1, 3, 4, 6 -hexa-0-acetylsucrose.

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