Addendum on the Anomeric Configuration of 3-D-Glycopyranosylbenzenes

As pointed out on page 276, the nomenclature of tetraacetyl-/S-D-glucopyranosylbenzene (IV), its anomer,66 and related compounds was based on their specific rotations in accordance with Hudson s conventions,63 and not on the actual stereochemical configurations of the phenyl group about the anomeric centers. Thus, for example, it has not been known if the rotationally designated /3-D-xylopyranosylbenzene (LX), actually possesses the configurational tram /3-structure (LXI), or cis a-structure (LXII). 

This problem has recently received attention, and it has been. shown that /8-D-xylopyranosylbenzene indeed has the 1,2-tram structure LXI.68 The structure proof rests on the fact that the configuration of the anomeric center in LX can be correlated with that of L-(+)-mandelic acid46 (68) W. A. Bonner and C. D. Hurd, J. Am. Chem. Soc., 78, 4290 (1951). 

Periodate oxidation of the ring in LXI led to sirupy n-2-phenyldigly-colaldehyde (LXIV), which in turn was oxidized with silver oxide to sirupy D-2-phenyldiglycolic acid (LXV). The latter was converted through its ester (LXVI), to crystalline D-(+)-2-phenyldiglycolamide (LXVII), m. p. 172-172.5°, [a]KD 102.2° (ethanol). 

Independent synthesis of the crystalline amide LXVII established its identity and its configurational relationship to L-(+)-mandelic acid. The latter acid was converted to ethyl L-(+)-mandelate (LXVIII), and the ether linkage introduced by reaction with ethyl bromoacetate in the presence of silver carbonate, under conditions such that Walden inversion was impossible. The resulting ethyl D-(+)-2-phenyldiglycolate (LXVI), was subjected to ammonolysis, giving a crystalline product, m. p. 174-174.5°, [a]26D 106.2°. This showed no mixed melting point depression and an identical infrared absorption spectrum with the sample of LXVII obtained from /3-D-xylopyranosylbenzene. The enantiomorphic l-(—)-2-phenyldiglycolamide was also prepared by identical synthetic steps from d-( —)-mandelic acid. 

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IV. Addendum on the Anomeric Configuration of /3-D-Glycopyranosylbenzenes. 282 V. Physical Properties of Products from Friedel-Crafts and Grignard Reactions 284... 

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