Anhydro rings scission

IV. The Scission of Anhydro Rings of the Ethylene Oxide Type. 47... 

It is to be noticed that although the anhydro ring of levoglucosan is stable to alkali (Tanret s preparative method consisted in the heating of aromatic jS-D-glucosides with aqueous alkali), it readily undergoes scission in the presence of acid. An isomeric glucose anhydride prepared in 1912 by E. Fischer showed, however, very different properties. 

Most investigations of the mechanism of ring scission have been made by studying the action of alkali on ethylene oxide anhydro sugars. These investigations will now be reviewed. 

The inference is that the hydrofuranol ring of XL can never be directly formed by the saponification of a 3-tosyl ester of D-glucose, but only indirectly by the intermediate formation and scission of an anhydro ring of the ethylene oxide type. The sequence of reactions involved in the conversion of methyl 3-tosyl-jS-D-gIueoside into methyl 3,6-anhydro-n-glucoside is shown by XXXVI to XL. 

Another method of synthesis of derivatives of 3-methyl-D-glucose lies in the scission of the anhydro-ring of 2,3-anhydro-D-allose derivatives with sodium methoxide, when the entry of the methoxyl group is accompanied by a Walden inversion on C3.82... 

The formation of anhydro-glycitols and the investigation of their structure and that of the products of their ring scission provide fascinating problems in structural organic chemistry and this structural aspect of the chemistry of anhydrides of polyhydric alcohols forms the mainstay of this article. 

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... 

Epoxide rings in sugars have been opened by the action of halogen acids. Both possible products of ring scission were observed in the reaction of methyl 2,3-anhydro-4,6-O-benzylidene-a-D-alloside 8 with hydrobromic... 

Scission of 5,6-anhydro-aldohexofuranoses and of four- to seven-membered anhydro rings (and use of a variety of reagents for such cleavage) has been discussed by Peat.311... 

If the secondary sulfonyloxy group is not isolated and is trans to a single, contiguous, free (or potentially free) secondary hydroxyl group, the intermediate formation of an anhydro ring occurs (as previously described in reference to anhydro-ring formation with sodium hydroxide and sodium methoxide see p. 172). Ammonia then causes ring scission as follows ... 

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