- Zeolite catalyzed selective deprotection of di- and tri-O-isopropylidene sugar acetals
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H-Beta zeolite, a microporous solid acid, is demonstrated to be an efficient catalyst for the selective deprotection of cyclic as well as acyclic O-isopropylidene sugar acetals derived from d-glucose, d-xylose, d-mannose, and d-mannitol in aqueous MeOH at room temperature. A notable observation is the conversion of d-mannitol triacetonide into 1,2:3,4-di-O-isopropylidene-d-mannitol (48%) and 3,4-O-isopropylidene-d-mannitol (36%) brought about in 6 h by H-beta zeolite and the non-occurrence of any hydrolysis in the case of H-ZSM-5 catalyzed reaction in 24 h under the same conditions.
- Bhaskar, Pallooru Muni,Mathiselvam, Manoharan,Loganathan, Duraikkannu
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p. 1801 - 1807
(2008/12/21)
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- Synthesis of some monodeoxy- and dideoxy-hexitols, and derivatives thereof, from D-glucono-1,5-lactone.
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Syntheses of 2-deoxy-D-arabino-hexitol (1), D-rhamnitol (2), 1,2-dideoxy-D-arabino-hexitol (3), 2,3-dideoxy-D-erythro-hexitol (4), and some derivatives thereof are described. These compounds were obtained by reductive sequences on various compounds formed from methyl 3,4:5,6-di-O-isopropylidene-D-gluconate (9).
- Regeling,Chittenden
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p. 261 - 268
(2007/10/02)
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- THE SYNTHESIS OF 1,2:5,6-DI-O-ISOPROPYLIDENE-D-MANNITOL: A COMPARATIVE STUDY
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Three different methods of acetonation of D-mannitol using (a) acetone and zinc chloride, (b) 2,2-dimethoxypropane, 1,2-dimethoxyethane, and tin(II)chloride, and (c) 2-methoxypropane, N,N-dimethylformamide, and p-toluenesulfonic acid were studied in detail and compared, using gas-liquid chromatographic techniques.In each reaction, isomeric diacetals are formed, but method a gives the 1,2:5,6-diacetal in the highest yield (63percent).Methods b and c give a more complex mixture of acetals than proposed in the literature, and both methods are less economical than a.A new 1,2:3,6:4,5-tri-O-isopropylidene-D-mannitol could be separated, and its graded hydrolysis was compared to that of the 1,2:3,4:5,6-triacetal.
- Kuszmann, Janos,Tomori, Eva,Meerwald, Ingrid
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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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- ISOPROPYLIDENATION OF D-MANNITOL UNDER NEUTRAL CONDITIONS
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Isopropylidenation of D-mannitol (2) under neutral conditions, by treatment with 2,2-dimethoxypropane in 1,2-dimethoxyethane, is described. 1,2:5,6-Di-O-isopropylidene-D-mannitol is the main equilibrium product, which does not undergo further substitution under the conditions used. 1,2:3,4:5,6-Tri-O-isopropylidene-D-mannitol, the other major product, was shown to be derived mainly from initial 3,4-substitution of 2.The presence of a difunctional ether, of suitable geometry, is a necessary requirement for the reaction.Some mechanistic aspects of the reaction are discussed.
- Chittenden, Gordon J. F.
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p. 219 - 226
(2007/10/02)
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