The title compounds 6 and 7 have been prepared from the known 2,3-di-U -benzyl-4,6-0 -benzylidene-o-galactose (18) and N'-acetyl-tri-O -benzyl-D-glucosamine oxime (29) in eight and six steps, respectively. The azidonitrile leading to the benzylated galacto-tetrazole 16 was prepared from 14 and cyclized under the conditions of its formation (Scheme I). The alcohol 13 was obtained by oxidation of 10 followed by reduction. Better yields and diastereoselectivities were realized, when the benzylidene-protected D-gafacto-alcohol 20 was subjected to oxidoreduction, yielding the L-altro -alcohol 22 via the ketone 21 (Scheme 2). Treatment of the corresponding tosylate 24 with NaN, yielded the tetrazole 25, which was deprotected to 6. The tetrabenzyl ether 16 (from 14, or from 25 via 27) was reduced to 28 and deprotected to give the known deoxygalactostatin 8 (Scheme 2). Oxidation of the hydroxynitrile 30, derived from 29, followed by reduction of 32 yielded mostly the L-ido-hydroxynitrile (Scheme 3), which was tosylated and treated with NaN3 to give the tetrazole 3Sa and its manno-isomer 36a, while AI(N,), yielded (E)-and (2)-38 (Scheme 4). The intermediate azide 39 was isolated besides 40 when NH,N,/DMF was used; thermolysis of 39 gave mostly 3Sa, which was deprotected to 7, besides some elimination product 41. Both 6 and 7 are stable in the pH range 1-10; at pH 12, 6 is unaffected but, 7 shows some epimerization to the manno-configurated isomer 43. The tetrazole 6 is a competitive inhibitor of the P-galactosidases from E. coli (4 = 1 p~, pH 6.8) and bovine liver (4 = 0.8 VM, pH 7.0); the N-acetyl-P-D-glucosaminidase from bovine kidney is competitively inhibited by 7 (4 % 0.2 p~, pH 4.1).Introduction. -We have designed the gluco-tetrazole 1 [I] [2] and its manno-epimer 2 [2] as neutral transition-state analogues for the inhibition of a-glucosidases and p-mannosidases, respectively. These tetrazoles possess a half-chair conformation in the solid state; in solution, 1 is a half-chair t6H7) and 2 a sofa (S7). A detailed kinetic study demonstrated that the inhibition is competitive and configurationally selective, and established these tetrahydrotetrazolopyridines (tetrahydropyridotetrazoles)') as transition-state analogues [2]. The inhibitory properties of the gluco-tetrazole 1 parallel those of D-glucono-l,5-lactone, but, unlike the corresponding lactones, 1 and 2 are stable towards hydrolysis over a wide range of pH values, an advantage for co-crystallization [9] and for their potential use as templates in the generation of catalytic antibodies [lo] [ll]. Additionally, reduction of the tetra-0-benzyl-protected tetrazole 3 is a key step in a new route to deoxynojirimycin [I].Galactose and N-acetylglucosamine derivatives possessing an sp2-hybridized anomeric center, such as galactono-1,5-1actam 4 [I21 and derivatives [ 131, the N-acetylglucosaminolactone 5 [14], the related lactone oximes [14] [15] and the lactam [14], are
Isosorbide is a biobased compound which could become in the near future an advantageous competitor of petroleum-derived components in the synthesis of polymers of different nature. When the reactivity of isosorbide is not enough, it can be successfully transformed into secondary building blocks, such as isosorbide bis(methyl carbonate), which provides extra functionalities for polymerization reactions with diols or diamines. The present review summarizes the possibilities for isosorbide as a green raw material to be used in the synthesis of polycarbonates and polyurethanes to obtain products of similar or enhanced properties to the commercial equivalents.
Currently, cathode manufacturing for lithium-ion batteries requires N-methyl-2-pyrrolidone (NMP) as a coating solvent. With concerns over its petrochemical origins and increasing scrutiny due to its undesirable toxicological profile, there is market demand for application-specific, less-regulated alternatives. Here, we evaluate γ-valerolactone (GVL), a promising green-candidate based on its closeness to NMP in the Hansen Solubility Space. It has successfully dissolved polyvinylidene fluoride (PVDF) at a temperature of 60 °C. We also show that the handling of lithium nickel cobalt manganese oxide (NCM 111) coating slurry prepared using GVL at 60 °C is comparable to NMP-based slurry at 25 °C. Cathode sheets (with dry mass loadings: 18 and 25 mg/cm 2 ) were manufactured by blade coating and drying (gas temperatures: 80 and 120 °C) in a custom-built batch coater with a convective drying unit. Adhesion and cell tests were performed to compare the resulting sheets. NMP-based films generally have higher adhesion strength than their GVL counterpart. We also report comparable resistance and columbic efficiency (after 1 cycle) for all cathodes, with slightly higher resistance for GVL dried harshly (i.e., 120 °C). Also, thinner NMP-based cathodes had better specific capacity during cycling than their GVL counterparts, irrespective of the drying temperature. However, thicker cathodes dried under higher throughput conditions (temperature of 120 °C) have comparable specific capacity after 100 cycles. Through this study, we highlight that GVL is a promising candidate currently available that merits further investigation.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
An efficient diastereo-and enantioselective synthesis of syn-2,3-disubstituted 1,4-diketones 4 is described. Key step of the procedure is the oxidative coupling of the metalated SAMP/RAMP-hydrazones 2 with iodine, followed by oxidative cleavage of the dimerized bishydrazones 3 with ozone and subsequent separation of the minor meso-isomer by chromatography. The d,l-isomers of the title 1,4diketones 4 are obtained in good overall yields (20 -64%) and high diastereo-and enantiomeric excesses (de ≥ 98%, ee = 80 − ≥95%).1,4-Diketones constitute an important class of compounds 1 , for instance as precursors of cyclopentanoids and five-membered heteroaromatics 2 . Although numerous synthetic routes to 1,4-diketones are known 3 , there are only a few asymmetric syntheses of the title compounds published so far 4 , and the direct approach via auxiliary controlled oxidative coupling has very recently been reported only for the related 1,4dicarboxylic acid derivatives 5-7 . The latter reports prompt us to disclose our own early results 8 on the asymmetric synthesis of 1,4-diketones via oxidative coupling of metalated SAMP/RAMP-hydrazones with iodine and subsequent removal of the auxiliary by ozonolysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.