1.6- Anhydro-a-D-galactofuranose

The failure of a compound to undergo periodate oxidation can not be regarded as positive proof that it contains no 1,2-glycol structures. If the glycol is securely locked in a trans position, oxidation has been shown not to occur. This resistance has been encountered in the bicyclic anhydro hexoses, for example, l,6-anhydro-/3-D-glucofuranoseM and 1,6-anhydro-a-D-galactofuranose.54 This work has already been summarized in this... 

Several routes to 1-deoxygalactonojirimycin (5) have been published to date. l,5-Dideoxy-l,5-imino-D-galactitol (5), the epimer of 1-deoxynojirimycin (1) at C-4, was st synthesized by Paulsen and co-workers in 1980 [24]. These workers employed 1,6-anhydro- a-o-galactofuranose (6) as the starting material. 

Selective tosylation of 1,6-anhydro-a-D-galactofuranose (167) is favored for position C-3 because of steric accessibility and affords tosylate 51. Treatment of 51 with base results in intramolecular displacement of the tosyloxy group by 5-hydroxyl group with the formation of 1,6 3,5-dianhydro-a-D-gulofuranose (168) the reaction involves closure of the oxetane and not the oxirane ring.246... 

P. Koll, J. Schulz, and U. Behrens, 1,6-Anhydrofuranosen. 9. Selektive Monotosylierung der 1,6-Anhydro-a-D-galactofuranose. Synthese und Bestimmung der Molekulstruktur der l,6 3,5-Dianhydro-a-D-gulofuranose, Chem. Ber., 112 (1979) 2068-2078. 

These considerations may be applied to an interpretation of the resistance of the trans 1,2-diols in l,6-anhydro-/3-D-glucofuranose and 1,6-an-hydro-a-D-galactofuranose. The bond angle32 for these hydroxyl groups apparently is near 120°, as is true in general for trans 1,2-diols on furan rings. Several examples are available of the oxidative cleavage of trans... 

The longest known compound in this series is 1,6-anhydro-a-D-galactofuranose (261). It is relatively easily obtainable, and is usually prepared by pyrolysis of D-galactose116,294,295,792 it can also be obtained by pyrolysis of lactose, melibiose, and raffinose.196,291 An alternative route consists in the reaction of 0.2 M hydrochloric acid, or 0.1 M sulfuric acid, with D-galactose.114,115 The anhydride 261 was originally mistaken for l,3-anhydro-/3-D-galactopyranose, because of... 

Oxidation of 1,6-anhydro-a-D-galactofuranose (30) with Pt02 afforded the ketone 31, which was treated with hydroxylamine to give a 3 1 mixture of isomeric oximes 32. Hy-drogenolysis of 32 in the presence of Raney nickel followed by treatment with CbzCl afforded the carbamates 33 and 34. Acid hydrolysis of 33 afforded 35, followed by hy-drogenolysis to give 4 (Scheme 6) " ... 

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