1.6- Anhydro cellobiose

Fig. 3.—A. Initial Slope Approximation to Determine the Initial, Nonselective, Spin-Lattice Relaxation Rate of H-S of 2,3 S,6-Di-0-isopropylidene-a-D-mannofuranose (2) in Me2SO-d Solution. (Points between 0.01 and l.SS s were selected for tracing the best straight line.) B. The Same as in A for H-1 of a Partially Deuterated Sample of 1,6-Anhydro- -cellobiose Hexaacetate (3). [Note that the relaxation of H-1 is strongly dependent on the choice of I value. An R (ns) value of 0.24s was obtained from the data points 0 t 5s, where a value of 0.18 s was obtained from the terminal decay 5 lOs (see text).]...

Fig. 6.—Allowed Rotational Conformation, Enclosed by Solid Line, of the Glucosidic Bond of 1,6-Anhydro- -cellobiose Hexaacetate (3), Calculated as a Function of the H-l,H-4 and H-l.H-5 Interatomic Distances. (Reproduced from Ref. 49.)...

Anhydro Cellobiose Benzyl Ether PFs Ring opening 4-j8-D-gluco- pyranosyl-(l- 6)- a-D-glucopyranan 70 14" + 77.8 (129)... 

The considerations involving comparisons of the structures of cellobiose and / -methylcellobioside with the structures of mercerized and native cellulose, respectively, when taken together with the additional observation that the basic repeat unit derived from the diffractometric studies is 10.3 A rather than 5.15 A, require that data relating to the structure of cellulose be reexamined with the constraint that the anhydro-cellobiose unit, rather than the anhydroglucose unit, is the basic repeat unit. To the author s knowledge, no efforts have been made to interpret... 

Interproton distances of 0-ceIIobiose (see Ref. 49) error 0.01 A. Interproton distances of 1,6-anhydro- -D-glucopyranose (see Ref. 49) error 0.01 A. Interproton distances of -cellobiose octaacetate (see Ref. 49) error 0.05 A. Interproton distances of 2,3,4-tri-0-acetyl-l,6-anhydro- -D-glucopyranose (see Ref. 49) error 0.05 A. Error calculations based on the errors of the measured quantities in Eqs. 18 and 21. Interproton distances calculated from the relaxation parameters of the methylene protons. 

Cellobiose octaacetate and 1,6-Anhydro-p-cellobiose hexaacetate are compared with respect to their glycosidic conformation [93, 94], For cellobiose octaacetate it was concluded that the conformation in solution is close to that one determined by X-ray crystal structure analysis to cp = 45° and i / = 16° (Fig. 5) whereas the 1,6-anhydro derivative is demonstrated by use of NOEs, relaxation data, and coupling constants 3JC>H to adopt torsional angles of = 25° and ]c = 45° respectively. 

The hexabenzyl derivatives of 1,6-anhydro maltose (37) and cellobiose (38) polymerized very sluggishly at — 60 °C. [36] Therefore, it appears that 1,6-anhydro disaccharide monomers with the (1 >3)-glycosidic linkage are less reactive than those with the (1 - 4)-glycosidic linkage. 

Although Fischer described a lactose phenylosazone anhydride in 1887, little attention was paid to substances of this type until 1935 when Diels and Meyer reported the isolation of monoanhydrides of D-glucose phenylosazone, D-galactose phenylosazone, D-xylose phenylosazone, L-arabinose phenylosazone, lactose phenylosazone, and cellobiose phenylosazone, as well as a dianhydride of maltose phenylosazone, by boiling the corresponding osazones in alcoholic solution with a little sulfuric acid. Because of the apparent identity of the D-glucose phenylosazone anhydride with the 3,6-anhydro-D-glucose phenylosazone of Fischer and Zach, Diels and Meyer formulated these compounds as 3,6-anhydrides. 

Cellobiose phenylosazone when treated by Diels method yielded a monoanhydride in the form of a hydrate. The same product was also obtained from cellobiose phenylosazone heptaacetate by deacetylation. The anhydride gave a pentaacetate proving that an oxide ring system was present, and structure XXXIII was proposed although the possibility of 1,3-anhydro- (1,5-oxide), 1,3-anhydro- (2,6-oxide) and 1,3-anhydro- (2,5-oxide) structures could not be rigidly excluded. 

L-a 2/lo-Hexose phenylosazone also gave the 3,6-anhydro-L-(2/a o-hexose derivative, and the phenylosazones from lactose and cellobiose yielded 3,6-anhydro-osazones, both with simultaneous Walden inversion on C-3. The D-galactose derivative, on the other hand, gave 3,6-anhydro-n-lyxo-hexose phenylosazone without inversion. 

---