- A new efficient access to glycono-1,4-lactones by oxidation of unprotected itols by catalytic hydrogen transfer with RhH(PPh3)4-benzalacetone system
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Treatment of unprotected pentitols and hexitols with RhH(PPh3)4-benzalacetone system leads exclusively to glycono-1,4-lactones in 60-96% yield.
- Isaac,Aizel,Stasik,Wadouachi,Beaupère
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p. 475 - 476
(2007/10/03)
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- Stereocontrol in organic synthesis using silicon-containing compounds. Syntheses of (±)-2-deoxyribonolactone and (±)-arabonolactone
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Samarium iodide reacts with methyl (Z)-3-dimethyl(4-methylphenyl)silylprop-2-enoate 5b to give dimethyl (3RS,4SR)-3,4-bis[dimethyl(4-methylphenyl)silyl]hexane-1,6-dioate 8b with high stereoselectivity. This meso diester can be converted into (3RS,4SR)-3,4-bis[dimethyl(4-methylphenyl)silyl]pentan-5-olide 16 by Dieckmann cyclisation, demethoxycarbonylation and Baeyer-Villiger reaction. Silyl-to-hydroxy conversion and relactonisation gave (±)-deoxyribonolactone, and anti-selective enolate hydroxylation followed by silyl-to-hydroxy conversion gave (±)-arabonolactone. An attempt to synthesise sugars with the relative configuration (3RS,4RS) was thwarted by an unprecedented retention of configuration at the migration origin in the cationic rearrangement of (3RS,4SR)-3,4-bis[dimethyl(4-methylphenyl)silyl]-5-hydroxypentanoic acid 28 to (3RS,4SR)-3,5-bis[dimethyl(4-methylphenyl)silyl]pentan-1,4-olide 30.
- Fleming, Ian,Ghosh, Sunil K.
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p. 2711 - 2720
(2007/10/03)
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- Stereoselective Samarium(II)-induced Coupling of β-Silylacrylic Esters: a Synthesis of (+/-)-2-Deoxyribonolactone
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Samarium iodide converts the β-silylacrylate 1c with high stereoselectivity into the racemic diester 2c, from which (+/-)deoxyribonolactone 11 can be prepared.
- Fleming, Ian,Ghosh, Sunil K.
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p. 1775 - 1777
(2007/10/02)
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- Synthesis of D-erythroascorbic acid from D-glucose
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Reaction of a 4:1 mixture of D-ribono- and D-arabinono-1,4-lactones with benzaldehyde and hydrochloric acid gave 59percent crystalline 3,4-O-benzylidene-D-ribono-1,5-lactone.This acetal was oxidized with manganese dioxide in acetone to its 2-keto-derivative (6) in 76percent yield.Acid-catalyzed methanolysis of 6 gave a syrupy mixture of products, which upon tautomerization in hot methanolic sodium acetate followed by removal of sodium ions gave 78percent D-erythroascorbic acid (7).The overall yield of 7 starting from D-glucose was 20percent.
- Gan, Li-Xian,Seib, Paul A.
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p. 117 - 126
(2007/10/02)
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