Aldoses, diethyl dithioacetals

Under such conditions secondary alcohols rarely afford homogeneous products, as the aldehydes expected as primary products too readily undergo further reactions. Exceptionally, a preparatively useful application has been found in the degradation of aldose diethyl dithioacetals these are oxidized by organic peracids or by hydrogen peroxide in the presence of ammonium molybdate to the disulfones which are cleaved at secondary alcohol groups by dilute ammonia solution.78,79 This method has been applied to acetyl-... 

The conformations of the peracetylated aldose diethyl dithioacetals in chloroform solution have been examined by n.m.r. spectroscopy, and the term sickle was introduced to designate the conformation generated from the extended, planar, zigzag form by rotation through 120° about an internal carbon-carbon bond. Such a sickle arrangement is adopted in solution by the D-xylose (8) and D-ribose (9) diethyl... 

In a survey " of the behavior of various classes of carbohydrate derivatives in c.i.m.s., it was found that the principal ion is the MH (isobutane) or M -I- NH (ammonia) ion, or a simple elimination product from it. The ammonia-mediated spectra feature M -I- NH f as the major ion with simple aldoses, their acetylated methyl glycosides, 1,6-anhydro-aldohexopyranoses (and their triacetates), and acetylated 1-thioaldoses. Aldose diethyl dithioacetals show M -I- NHf — EtSH as the principal ion, whereas this ion for aldehydo-aldose peracetates is MH — AcOH. 

The reaction has recently been used to prepare 2-deoxyaldonitriles from aldose diethyl dithioacetals, as shown in equation (II) for the o-glucose derivative. ... 

The isopropylidenation of aldose trimethylene dithioacetals is covered in Chapter 6 and the acetolysis of aldose diethyl dithioacetals in Chapter 7. The C-C-l(C-2 bond cleavage of the a-oxoketene dithioacetal 7 on exposure to mineral acid is referred to in Chapters 13 and 14. The phenylthio precursor 8 of 2-keto-3-deoxy-D-flraZ //io-heptonic acid has been prepared by chain-extension of 2,3 4,5-di-O-cyclohexylidene-D-arabinose with PhSCH2C02Me, followed by de-protection. ... 

Scheme 47. Partial fragmentation of 0-methyl aldose diethyl dithioacetals.

Scheme 55. Partial fragmentation of a 3-acetamido-3-deoxy aldose diethyl dithioacetal showing fragment A.

H. Zinner, G. Rembarz, and H. Klocking, Isopropyliden-verbindungen der D-arabinose-mercaptale, Chem. Ber. 90 2688 (1957) P. A. J. Gorin, Acetonation of aldose diethyl dithio-acetals. Can. J. Chem. 43 21X18 (1965) D. G. Lance and J. K. N. Jones, Acetonation of D-xylose diethyl dithioacetal, Can. J. Chem. 45 1533 (1967). 

Acetolysis of the diethyl dithioacetals of a nmnber of aldoses has been found to give the aldehydo-aldose peracetates. ... 

Displacements Catalyzed by Adds.—The acid-catalyzed mercaptala-tion reaction with ethanethiol normally leads to the aldose diethyl dithio-acetal, but, in anhydrous reaction media, further ethylthio substituents may be introduced into the molecule, usually at C-2. Brigl and coworkers found that ethanethiol and hydrogen chloride convert 3,4,5,6-tetra-O-benzoyl-D-glucose diethyl dithioacetal into 3,4,5,6-tetra-O-benz-oyl-2-)S-ethyl-2-thio-D-glucose (mannose) diethyl dithioacetal. The diethyl... 

When the paromobiosamine fraction is W-benzoylated and then hydrolyzed with dilute acid, D-ribose is one of the products. More-vigorous hydrolysis destroys the D-ribose but yields a diaminodideoxyhexose which was called paromose. A study of the products of periodate oxidation of paromose, of its di-W-acetyl derivative, and of the borohydride reduction product of the latter, revealed that paromose is a 2,6-diamino-2,6-di-deoxyhexose. In a preliminary report, Haskell and Hanessian have presented degradative evidence which establishes the stereochemical structure of paromose as that of 2,6-diamino-2,6-dideoxy-L-idose (7). Their ingenious application of the degradation described by MacDonald and Fischer and by Hough and coworkers of the 1, l-bis(ethanesulfonyl) derivatives of aldoses enabled Haskell and Hanessian to obtain, from iV,fV -diacetylparomose diethyl dithioacetal, a product which they identi-... 

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