Oxidation of 2,3-0-isopropylidene-8-L-rhamnose (I) with hypoiodite, follo\ved by periodate cleavage of the derived aIdonic acid, affords 2,3-0-isopropylidene-L-ery~huotetruroiii acid.Reduction of I with sodium borohydride and periodate oxidation of the resulting glycitol gives 2,3-0-isopropylidene-L-erythrose. Both products have been obtained in high yield, and are readily hydroIyzed to L-erythrotetruronic acid and L-erythrose, respectively.Methyl a-and 8-D-erythro-and D-threo-tetrofuranosides have been prepared by the Fischer glycoside synthesis from D-erythrose-and D-threose-formates, respectively. A notable anomeric difference in the lead tetraacetate oxidation behavior of the methyl D-threosides has been observed, the 0-anomer being more reactive than the a-anomer.111 continuing earlier studies in this laboratory on the chenlistry of the tetrose sugars (1, 2, 3, 4) several new tetrose derivatives have been prepared and are described in the current paper.Stepwise degradation of D-glucuronic and D-galacturonic acids t o D-erythro-and D-threo-tetruronic acids, respectively, by lead tetraacetate oxidation has been described previously (3). Since the L-isomers of these hexuronic acids are rare compounds, they do not provide practical sources of the L-tetruronic acids. The L-threo-isomer has been prepared by selective reduction of 2,3-di-0-acetyl-L-tartaric anhydride ( 5 ) and by oxidative degradation of D-glucosaccharo-7-lactone (6), but the L-erythro-acid does not appear to have been reported. I n the current paper a inethocl is described for preparing L-erythrotetruronic acid from readily available 2,3-0-isopropylidene-~-rl~a1~~nose (7) (I).The latter derivative also has been utilized to prepare L-erythrose in high yield.Xcetonatio~l of L-rhamnose in the presence of hydrogen chloride (7) appears to yield the 2,3-0-isopropylidene derivative allnost exclusively. Two crystalline forms of monoacetone L-rhamnose have been described (8,9) but only the p-anomer (9) has been isolated in the present study. The isopropylidene derivative (I) was oxidized with hypoiodite (10) t o the L-rhamnonate (11) and the latter, which was not isolated, \\-as degraded by perioclate cleavage. From the reaction misture crystalline 2,3-0-isopropylidene-L-erythrotetruronic acid (111) was isolated in about 75% yield. Chromatographically pure L-erythrotetruronic acid was readily obtained by autohydrolysis of 111 in aqueous solution.Reduction of isopi-opylidene-P-L-rhamnose (I) to the rhamnitol derivative (IV), followed by periodate oxidation, afforded crystalline 2,3-0-isopropylidene-L-erythrose (V) in about 80% yield. The L-glycitol derivative (IV) was obtained as a syrup by catalytic hydrogenation but, \\-it11 socliunl borohydride reduction, attempts to isolate it resulted in partial hydrolysis of the isopropylidelle group. For preparation of V, however, it was most convenient to carry out the reduction \\lit11 borohydride and, after neutralizing the reaction mixture, to continue directly \\-it11 the periodate cleavage step. Such a...

No abstract

Arylthioureas, when heated in chlorobenzene at 150" for 5-10 hr., undergo fission to give good yields of aryl isothiocyanates containing 1, 2, 3, and 4 aromatic rings. The mechanism of the reaction has been investigated. METHODS of preparation of aryl isothiocyanates 1 include (a) the use of thiocarbonyl chloride or its precursor thiocarbonyl tetrachloride (the latter reaction fails with naplithj*l compounds 3), (b) acid-induced fission of an NN'-diarylthiourea, iiivolving the loss of 1 mol. of amine, and (c) decomposition of an ammonium aryldithi~carbamate,~ the last method giving low yields for naphthyl and other compound^.^It has now been found that arylthioureas, when heated in a suitable solvent at 150°, undergo fission into ammonia and the aryl isothiocyanate. No isothiocyanate was obtained on attempted vacuum-distillation of 4-diphenylyl-or a-naphthyl-thiourea without a solvent.the methods of de Clermont 8 and Bertram failed for the latter substance. N-4-Diphenylylthiourea was obtainable by either method, or from N-4-diphenylylammoniuni thiocyanate. The related N-4-diphenylyl-S-methylisothiourea, ammonium N-4-diphenylyldithiocarbamate, and N-Pdiphenylylguanidine were prepared, the last by heating N-4-diphen ylyldiguanide.When N-4-diphenylylthiourea was heated in solvents of various b. p.s, chlorobenzene gave optimum yields of N-4-diphenylyl isothiocyanate ; 1 : 2-dichlorobenzene also aff ordecl the desired product, though in smaller yield, while nitrobenzene or 1 : 2 : 4trichlorobenzene gave no isothiocyanate. N-4-Diphenylyl isothiocyanate had m. p. 63.5--64-5", though Desai, Hunter, and Kureishy lo claim m. p. 119-120".Brewster and Horner 11 claim preparation of this isothiocyanate by 3 hours' boiling of the "'-diary1 thiourea with acetic anhydride. This procedure in our hands gave NN-diacetyl-4-aminodipheny1, m. p. 118.5-11 9", and NN'-diacetyl-NN'-bis-4-diphenylylurea, hydrolysed by alkali to 4-acetamidodiphenyl. Reaction of acetic anhydride with the isothiocyanate afforded the same products. Werner l2 reported the action of acetic anhydride on NN'-diphenylthiourea to give phenyl isothiocyanate in 96,37,7, and 0% yield after 5,30,45, and 60 minutes' boiling respectively, but did not identify the product of decomposition. This isothiocyanate is known l3 to give the N-acylaniline and diphenylurea when treated with acetic or formic acid, while benzoic anhydride gives NN-diben~oylaniline.1~ The mechanism of isothiocyanate formation was investigated by using a-naphthylthiourea. The rate of evolution of ammonia a t 150°, measured during 6 hr., gave the results shown in the Figure . A plot of log,, CAo/(Cao -CNH,) (where CAo = initial concentration of thiourea and CNH, = concentration of ammonia at time t ) was linear only for 1.5 hr., although the " half-time " of the reaction (65 min.) was independent of the magnitude of Cbo. The possibility of the reaction's occurring in three successive steps (a), (b), and (c), with the intermediate formation of a dithiobiuret, could be dismissed in view of the failure of ...

The oxidation of D-glucose 6-phosphate by lead tetraacetate in cold acetic–propionic acid produces D-erythrose 4-phosphate contaminated with a small proportion of D-glyceraldehyde 3-phosphate. The product is a suitable substrate for certain enzymic studies, as illustrated by its use in the assay of transaldolase and transketolase. D-Erythritol 4-phosphate may readily be obtained in high yield by reducing the crude oxidation mixture with sodium borohydride. Oxidation of D-fructose 6-phosphate with 1 mole of lead tetraacetate gives chiefly D-erythrose 4-phosphate, whereas oxidation with 2 moles produces mainly D-glyceraldehyde 3-phosphate. The stability of D-erythrose 4-phosphate under a variety of conditions was also examined.

The oxidation of D-glucose 6-phosphate by lead tetraacetate in cold acetic–propionic acid produces D-erythrose 4-phosphate contaminated with a small proportion of D-glyceraldehyde 3-phosphate. The product is a suitable substrate for certain enzymic studies, as illustrated by its use in the assay of transaldolase and transketolase. D-Erythritol 4-phosphate may readily be obtained in high yield by reducing the crude oxidation mixture with sodium borohydride. Oxidation of D-fructose 6-phosphate with 1 mole of lead tetraacetate gives chiefly D-erythrose 4-phosphate, whereas oxidation with 2 moles produces mainly D-glyceraldehyde 3-phosphate. The stability of D-erythrose 4-phosphate under a variety of conditions was also examined.