01074nas a2200157   4500008004100000022001400041245014100055210006900196260000800265300001200273490000700285520044800292100002000740700002800760856012800788       2018                        eng d  a1477-052000aHydroxyl directed C-arylation: synthesis of 3-hydroxyflavones and 2-phenyl-3-hydroxy pyran-4-ones under transition-metal free conditions0 aHydroxyl directed Carylation synthesis of 3hydroxyflavones and 2  cJAN  a444-4510 v163 a<p>An efficient, transition-metal free and direct C-arylation of 3-hydroxychromone moieties in the presence of a base, air as an oxidant and arylhydrazines as arylating agents to furnish highly biologically active flavonols or 3-hydroxyflavones has been developed. We have further extended our methodology for the C-arylation of the 5-hydroxy pyran-4-one moiety. The role of the free hydroxyl group towards C-arylation has been delineated.</p>1 aPaula, Sayantan1 aBhattacharya, Asish, K.  uhttps://library.ncl.res.in/content/hydroxyl-directed-c-arylation-synthesis-3-hydroxyflavones-and-2-phenyl-3-hydroxy-pyran-401903nas a2200193   4500008004100000022001400041245016200055210006900217260000800286520116300294653001501457653001201472653001601484653001401500653001301514100002401527700002801551856013001579       2019                        eng d  a2193-580700aHemiketal-keto tautomerism in 2-deoxy-delta-lactones mediated by 2-lithiothiazole in solution state: a formal synthesis of DAH, Kamusol and their C-5 Epimers0 aHemiketalketo tautomerism in 2deoxydeltalactones mediated by 2li  cOCT3 a<p>The reactions of 2-lithiothiazole on 3,4,6-tri-O-benzyl-2-deoxyglyconolactones have been studied, which resulted in the formation of two products, major (3,4,6-tri-O-benzyl-2-deoxy-1-(2-thiazolyl) glycal) and minor products 3,4,6-tri-O-benzyl-2-deoxy-1-(2-thiazolyl) glycal hemiketal. The hemiketal-keto tautomerism in solution was observed in the minor product. The tautomerism has been studied in various organic solvents and their ratios have been determined by H-1 NMR spectroscopy. The major product from the reaction of 2-lithiothiazole with 2-deoxygluconolactone was utilized for the synthesis of 3-deoxy-D-arabino-2-heptulosonic acid DAH 4 a and 3-deoxy-D-arabino-2-heptulopyranose commonly known natural product kamusol 6 a via acid catalyzed hydration followed by stereoselective methyl glycoside bond formation. Similarly, major product from 2-deoxygalactonolactone furnished 5-epi-DAH 4 b (C-5 epimer of 4 a) and 5-epi-kamusol 6 b (C-5 epimer of 6 a). The minor product has also been utilized for the synthesis of DAH 4 a, 5-epi-DAH 4 b, kamusol 6 a and 5-epi-kamusol 6 b through a common intermediate, alpha-methyl glycosylated product.</p>
10ahemiketals10aKetones10atautomerism10athiazoles10aumpolung1 aChand, Hemender, R.1 aBhattacharya, Asish, K.  uhttps://library.ncl.res.in/content/hemiketal-keto-tautomerism-2-deoxy-delta-lactones-mediated-2-lithiothiazole-solution-state