R. Stuart Tipson

Cyclic acetals of ketoses : Part IV. Re-investigation of the oxidation of 1,2:4,5-DI-O-isopropylidene-β-D-fructopyranose with methyl sulfoxide—acetic anhydride

Abstract For the preparation of pure D -psicose ( 5a ) via oxidation of 1,2:4,5-di- O -isopropylidene-β- D -fructopyranose ( 2a ), the latter must be free from its 2,3:4,5 isomer ( 6a ), which is oxidized to the corresponding aldosulose acetal. Pure 1,2:4,5-di- O -isopropylidene-β- D - erythro -2,3-hexodiulo-2,6-pyranose ( 3 ) undergoes stereospecific reduction with sodium borohydride to give only 1,2:4,5-di- O -isopropylidene-β- D - ribo -hexulopyranose ( 4a ), which exists as two different crystal modifications. Compounds 3 and 4a have been characterized, and discrepancies in the literature have been explained.

Reaction of some sulfonic esters of D-mannitol with methoxide; synthesis of 2,3:4,5-dianhydro-D-iditol

Abstract 3,4-Di- O -(methylsulfonyl)- and 3,4-di- O - p -tolylsulfonyl- D -mannitol and their 1,2,5,6-tetraacetates have been synthesized and crystallized. By the action of an excess of methanolic barium methoxide during 2 h at 25°, each of these compounds is converted into 2,3:4,5-dianhydro- D -iditol, the structure of which is assigned on the basis of chemical and physical properties, including n.m.r. spectroscopic evidence.

Synthesis of the two d-2-pentuloses. : New derivatives of d-erythro-pentulose

Abstract The syrupy mixture of eight pentoses obtained by boiling a solution of either d -xylose ( 1 ) or d -arabinose ( 2 ) in pyridine for 4.5 h was freed of the four d -aldopentoses. The resulting mixture of four d -pentuloses was resolved by condensation with acetone, followed by partition between solvents or by distillation; in this way, crystalline 2,3- O -isopropylidene-β- d - O -isopropylidene- d - erythro -pentulofuranose ( 14 ) from 2 . Each of the isomerizations yielded a small proportion of the epimeric d -2-pentulose, but the proportions of the d -3-pentuloses were much lower. The diacetal 14 was partially hydrolyzed, with dilute acid, to 3,4- O -isopropylidene- d - erythro -pentulofuranose ( 17 ), the α- d anomer of which was obtained in crystalline form. The structure of 17 was proved by oxidation with periodate, to give the known, crystalline 2,3- O -isopropylidene- d -erythrono-1,4-lactone. The anomers of the 1,3,4-triacetate and 1,3,4-tribenzoate of methyl d - erythro -pentulofuranoside were prepared, and characterized by specific optical rotation and n.m.r. spectroscopic evidence.

Conformational analysis of acylated 1,1-bis(acylamido)-1-deoxypentitols by fourier-transform, p.m.r. spectroscopy

Abstract The conformations of eight acylated 1,1-bis(acylamido)-1-deoxypentitols in solution have been studied by pulse, Fourier-transform, p.m.r. spectroscopy at 90 Mhz. The arabino and lyxo derivatives adopt the zigzag conformation, whereas the ribo and xylo derivatives favor different sickle conformations. The validity of the conformational assignments of these derivatives by the p.m.r. method is discussed. The relative merits and accuracy of the continuous-wave and pulse-Fourier p.m.r. spectroscopic methods in the conformational analysis of carbohydrates are appraised, and the applicability of the exponential-filtering technique to enhancement of either the sensitivity or the resolution of their spectra is demonstrated.