- Novel preparation method for gemcitabine hydrochloride
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The invention discloses a preparation method for gemcitabine hydrochloride. The preparation method comprises the steps: carrying out condensation, cracking and addition on D-mannitol serving as an initial raw material, and protecting hydroxyl by TESC1 to prepare an intermediate; and after carrying out condensation on the intermediate and cytosine under the catalysis of chiral phosphoric acid, carrying out salification to prepare gemcitabine hydrochloride. The preparation method has the advantages that the reaction steps are reduced, and the cost is reduced. Due to the use of the chiral phosphoric acid, the proportion of a required beta structure is greatly increased, the ratio of beta to alpha can reach 9:1, and the yield is increased. The chiral phosphoric acid belongs to an organic acidand is recyclable, little to environment pollution and particularly suitable for industrial production of gemcitabine hydrochloride.
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Paragraph 0008; 0013
(2018/04/21)
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- Synthesis of a trihydroxylated aminoazepane from D-glucitol by an intramolecular aziridine ring opening
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Transformation of D-glucitol into its 1,6-diazido derivative allowed its conversion into the polyhydroxylated aminoazepane ring in a one-pot reaction using Ph3P and H2O. Georg Thieme Verlag Stuttgart.
- Valle, Marcelo Siqueira,Braga, Raquel Marques
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scheme or table
p. 2874 - 2876
(2009/05/28)
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- Free-Radical Chemistry of Imines
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Aryl radicals bearing an aldimino functional group as part of an ortho substituent cyclized by addition to C and/or N of the imino group.When the choice was between 5-exo closure to C and 6-endo closure to N, the former predominated.However, 6-endo closure to C predominated over 5-exo cyclization to N in isomeric imines.Absolute values of cyclization rate constants were determined and an explanation for the unusual 6-endo preference is offered.Chiral induction in 6-endo cyclization to C of an aldimine from D-glyceraldehyde acetonide was observed, and its sense was determined.
- Tomaszewski, Miroslaw J.,Warkentin, John,Werstiuk, Nick H.
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p. 291 - 322
(2007/10/02)
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- New chiral phosphines derived from carbohydrates: Synthesis, characterization and application in hydrogenation
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Synthesis and characterization of new chiral phosphines derived from carbohydrates such as D-mannitol and D-sorbitol have been described.The chiral phosphine complexes display moderate enantioselectivity in the asymmetric hydrogenation of methyl ester of benzamidocinnamic acid.
- Choudary, B. M.,Sarma, M. Ravichandra,Prasad, A. Durga,Narender, N.
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p. 152 - 155
(2007/10/02)
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- SOME ASPECTS OF THE ISOPROPYLIDENATION OF D-GLUCITOL UNDER NEUTRAL CONDITIONS
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Isopropylidenation of D-glucitol (1) under neutral conditions, by treatment with 2,2-dimethoxypropane in 1,2-dimethoxyethane, has been studied.An improved procedure for the isolation of 1,2:5,6-di-O-isopropylidene-D-glucitol, the main equilibrium product, by direct crystallisation or via the 3,4-dibenzoate is described.Some aspects of the reaction are discussed and compared with results obtained previously from the isopropylidenation of 1 in the presence of zinc chloride.
- Chittenden, Gordon J. F.
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- Acyclic Stereoselection. 12. Double Stereodifferentiation with Mutual Kinetic Resolution. A Superior Class of Reagents for Control of Cram's Rule Stereoselection in Synthesis of erythro-α-Alkyl-β-hydroxy Carboxylic Acids from Chiral Aldehydes
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Chiral α- ketones 7-9 have been prepared and their aldol condesations studied.Compound 8 shows from good to excellent inherent diastereoface selectivity in reactions with achiral aldehydes.Stereoselectivity is related to the size of the alkyl group attached to the aldehyde carbonyl; highest selectivity is observed with diphenylacetaldehyde (>10:1) and pivaldehyde (>19:1).Ketone 8 also shows high diastereoface selectivity in its reactions with chiral, racemic aldehydes 21, 25, 29, and 17, only one stereoisomeric aldol being obtained in each case.Furthermore, the four aforementioned aldehydes show much higher diastereoface selectivity with ketone 8 than they do with the related ketone 1.As a result, the reactions of racemic 8 with these chiral, racemic aldehydes show a high degree of "mutual kinetic resolution".In fact, the rate of the (R)-enolate plus (R)-aldehyde condensation is at least 35 times the rate of the (R)-enolate plus (S)-aldehyde condensation.It is shown by simple logical argument that such mutual kinetic resolution is expected in reactions between two chiral racemic compounds and that the magnitude of the effect should be proportional to the inherent diastereoselectivity shown by each compound in its reaction with achiral reaction partners.Thus, reagents such as 8 can be used to obtain the benefits of double stereodifferentiation even in the racemic form.As an application of the chemistry developed, (+/-)-blastmycinone (47) has been prepared in four steps from ketone 9 (20percent overall yield).
- Heathcock, Clayton H.,Pirrung, Michael C.,Lampe, John,Buse, Charles T.,Young, Steven D.
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p. 2290 - 2300
(2007/10/02)
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- REINVESTIGATION OF THE ACETALATION OF D-GLUCITOL WITH ACETONE-ZINC CHLORIDE
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The acetonation of D-glucitol in the presence of zinc chloride has been studied in detail by gas-liquid chromatographic techniques.From among the 12 different peaks, those belonging to the 1,2:3,4:5,6-tri-, 1,2:3,5:4,6-tri-, 3,4:5,6-di-, 2,3:5,6-di-, 1,2:3,4-di-, 1,2:5,6-di-, 1,2:4,6-di-, 1,2-mono-, 2,3-mono-, 3,4-mono-, and 5,6-mono-acetals could be identified.The course of the reaction was also studied by g.l.c.From the time dependent ratio of the different acetals, it could be concluded that the reaction is kinetically controlled at the beginning, when terminal acetals are mainly formed.In the thermodinamically controlled equilibrium, reached after 5 days, the 1,2:3,4:5,6-tri- and the 2,3:5,6-di-acetal are present in almost equal proportions.The structure of the (new) 1,2:3,5:4,6-triacetal was established by mass-spectrometric and 13C-n.m.r. investigation.
- Kuszmann, Janos,Sohar, Pal,Horvath, Gyula,Tomori, Eva,Idei, Miklos
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p. 243 - 254
(2007/10/02)
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