3,4-anhydro-, proton magnetic resonance

The configuration at C-2 was established by comparison with the optical activities of 1,5-anhydro-D-mannitol and -D-glucitol and the proton magnetic resonance (p.m.r.) spectra of their acetates.31(b) This reaction is useful for the preparation of C-2 substituted derivatives, but the configuration at C-2 of the products must then be established. 

P. C. Wollwage and P. A. Seib, Preparation and proton magnetic resonance spectra of the methyl ethers of l,6-anhydro-/fi)-glucopyranose, J. Chem. Soc. C, (1971) 3143-3155. 

L. D. Hall and L. Hough, Proton magnetic resonance spectra of 2,3,4-tri-0-acetyl-l,6-anhydro-D-hexopyranoses A long-range coupling, Proc. Chem. Soc., (1962) 382. 

Fig. 1.—Proton Magnetic Resonance Spectrum of 5,6-Anhydro-l,2-0-i8opropylidene-a-D-glucofuranose. (A, in neutral acetone B, in acidified acetone. )...

The types of free hydroxyl groups present were determined for several acetals of sedoheptulosan by measuring the proton magnetic resonance spectrum of the compound in dry methyl sulfoxide-dg and observing the multiplicity of the signal caused by the hydroxyl protons. The p.m.r. spectrum of 2,7-anhydro-4,5-0-isopropylidene-jS-D-flltro-heptulopyranose (74) ( isopropylidene-sedoheptulosan ) shows a doublet (/ = 7 Hz) at r 4.90 and a triplet (J = 6.5 Hz) at t 5.33 ... 

Acid hydrolysis of 5-amino-5-deoxy-l,2-0-isopropylidene-o -D-xy-lofuranose (15) might be expected to afiFord 5-amino-5-deoxy-D-xylose, but instead, at 70 , 3-pyridinol (21) is the main product. If the acid hydrolysis of compound 15 is conducted at room temperature, there is obtained, besides 3-pyridinol (21), the crystalline hydrochloride of l-amino-l,5-anhydro-l-deoxy-D-fhreo-pentulose hydrate (22). The crystalline hydrate exhibits no carbonyl band in its infrared and ultraviolet spectra. The water content cannot be removed without decomposition of the compound, and is, therefore, water of constitution. The nuclear magnetic resonance spectrum of 22 lacks the signal characteristic of an anomeric proton. The free ketone group is, however, detectable by the preparation of a (2,4-dinitrophenyl)-hydrazone. 

Fig. 6.—Nuclear Magnetic Resonance Signals for the Anomeric Protons of 5,6-Bis(acetamido)-l,6-anhydro-5,6-dideoxy-/8-L-idopyranose at Various Temperatures.

Previously, only one-dimensional nuclear magnetic resonance (NMR) spectroscopic data had been reported for the 3,6-anhydroglucal 7 in the literature [17]. We carried out additional two-dimensional NMR experiments ( H- H COSY, NOESY, and HMQC) to fully characterize the compound. The proposed anhydro structure was supported by the observation of long-range coupling between the vinylic proton (C2) and the bridgehead proton (C4 1.5 Hz). We were also able to obtain crystals for 3,6-anhydroglucal 7 and an x-ray structure was obtained [26]. 

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