2,25:5-anhydro structure

NMR, 4, 575 Erythritol, 1,4-anhydro-structure, 4, 546 Erythromycin antibacterial veterinary use, 1, 206 as pharmaceutical, 1, 153 synthesis, 1, 480 Erythropterin biosynthesis, 3, 321 occurence, 3, 323 structure, 3, 276 synthesis, 3, 289 Erythropterin, 3,5-dimethyl-methyl ester synthesis, 3, 303 Erythrosine application, 3, 879 Esculetin... 

Brigl and Griiner45 reported the isolation of three products when 1,6-di-O-benzoyl-D-mannitol (29) was heated in boiling 1,1,2,2-tet-rachloroethane in the presence of p-toluenesulfonic acid as the catalyst. These compounds were assigned mono- and di-anhydro structures, and were later shown by Hockett and coworkers46,47 to be 1,4-anhydro-D-mannitol dibenzoate (30), l,4 3,6-dianhydro-D-man-nitol dibenzoate (31), and 2,5-anhydro-l,6-di-0-benzoyl-D-glucitol (32). The latter compound, which can be readily isolated from the... 

High-held H and 13C NMR spectra of aqueous solution of D-xylo-hexos-5-ulose (242) have provided evidence for the presence of at least six isomeric forms and one anhydro form. The dominant isomeric form was the /f-pyranose 242a (67%) with the next most abundant form being the anhydro structure 242c (18%). The a- and /My4-furanoses (242d,e) and 1-aldehydrol /1-5,2-furanose structure (242f) were also observed.459... 

The high reactivity of 34 relative to 36 is probably due to its 2,4-dideoxygenated anhydro structure. Both the acetal oxygen of the monomer and the trialkyloxonium ion of the growing terminal in 34 are less sterically hindered and more basic and nucleophilic than those in the corresponding dibenzyloxylated compound (36). 

The 2 -0-p-tolylsulfonyl derivative of 8-hydroxyadenosine underwent intramolecular sulfonate displacement when heated at 100-105° with sodium benzoate in N V-dimethylformamide, and the 2, 8-anhydro structure (170) was indicated.434 A derivative of2, 8-anhydro-guanosine (171) was obtained by a similar method.435... 

Compounds of this class are characterized by their instability in acidic solutions, in which hydrolysis of the enolic ether grouping is followed by an elimination, to give unsaturated, osone derivatives, namely, 3,4-dideoxy-D-j(lj/cero-hex-3-enos-2-ulose (85, R = H) and its 6-methyl ether (85, R = Me), which are unstable, undergo ring contraction, and lose the elements of water to give, ultimately, 5-(hydroxymethyl)- and 5-(raethoxy-methyl)-2-furaldehyde (86, R = H or Me). For the monomethyl ether (84, R = H), this decomposition is complicated by a side reaction probably involving the formation of 3,6-anhydro structures. 

Previously, only one-dimensional nuclear magnetic resonance (NMR) spectroscopic data had been reported for the 3,6-anhydroglucal 7 in the literature [17]. We carried out additional two-dimensional NMR experiments ( H- H COSY, NOESY, and HMQC) to fully characterize the compound. The proposed anhydro structure was supported by the observation of long-range coupling between the vinylic proton (C2) and the bridgehead proton (C4 1.5 Hz). We were also able to obtain crystals for 3,6-anhydroglucal 7 and an x-ray structure was obtained [26]. 

For our bicyclic anhydro structure 7, treatment with methanol and with 1.5 equivalents of A-iodosuccinimide (NIS) in acetonitrile gave an inseparable mixture of diastereomeric a-manno, p-manno, and p-gluco-2-deoxy-2-iodomethylglycosides 8a-c (1 1.5 5.2 by proton NMR integration) in a 93% yield (Scheme 12.4). Contrary... 

Benzothiazolylium salts, 2-alkoxy-3-methyl-reactions, 6, 289 Benzothiazolylium salts, 3-alkyl-deprotonation, 6, 262 Benzothiazolylium salts, 2,3-dimethyl-anhydro base structure, 6, 238 reactions... 

Oxazolium hydroxide, anhydro-2-m-bromophenyl-5-hydroxy-3-methyl-4-trifluoroacetyl-X-ray structure, 6, 180 Oxazolium hydroxide, anhydro-4-hydroxy-cycloaddition reactions, 6, 208 IR spectra, 6, 186 mesoionic structures, 6, 179 tautomerism, 6, 185 reactions, 6, 206-211 synthesis, 6, 225... 

Pteridine, 2-amino-4,6,7-trimethyl-basicity, 3, 267 Pteridine, 2,2 -anhydro-nucleosides, structure, 3, 283 Pteridine, 2,5 -anhydro-nucleosides structure, 3, 283 Pteridine, 6-aryl-synthesis, 3, 316 Pteridine, 7-aryl-synthesis, 3, 314... 

Thiazolo[3,2-a]pyridinium hydroxide, anhydro-2a,3/3-dicarboxy-2,3-dihydro-5-methyl-structure, 6, 672 X-ray diffraction, 6, 670... 

Recent work has justified the suspicions that the methylated cinnolones had been allocated the incorrect structures. D. E. Ames and H. Z. Kucharska [J. Chem. Soc. 4924 (1963)] have shown that the compound previously believed to be l-methyl-4-cinnolone is the dipolar anhydro-base of 4-hydroxy-2-methyl-cinnolinium hydroxide. It is likely, therefore, that those cinnoline salts whose structures had been based upon the presumed l-methyl-4-cinnolones are, in fact, 2-salts of structure 56. (Cf. p. 28.)... 

When a jo /r-A-alkylcarbolinium salt, unsubstituted at the ind-N atom, is treated with strong alkali, a yellow to deep orange, strongly basic solid separates. Although such products almost invariably give poor microanalytical values they can be shown to be derived from the quaternary hydroxide by loss of a molecule of water—hence the name anhydro-bases or anhydronium bases.All four carbolines form anhydro-bases e.g., j9 /r-A-methyl-j8-carbolinium iodide (419) gives 420. Most of the evidence bearing on the structures of these bases has been summarized, and discussion will therefore be limited to a few of the recent aspects of the chemistry of these compounds. 

Support for this suggestion comes from many quarters. Reduction of the jS-carboline anhydro-bases with sodium and alcohol or with tin and hydrochloric acid gives the 1,2,3,4-tetrahydro derivatives, as does catalytic reduction over platinum oxide in an alkaline medium. On the other hand, catalytic reduction with platinum oxide in acetic acid results in the formation of the 5,6,7,8-tetrahydro-j3-carbolinium derivatives (see Section III,A,2,a). It should be noted, however, that reduction of pyrido[l,2-6]indazole, in which the dipolar structure 211 is the main contributor to the resonance hybrid, could not be effected with hydrogen in the presence of Adams catalyst. 

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