- Mild and facile procedure for clay-catalyzed acetonide protection and deprotection of N(Boc)-amino alcohols and protection of 1,2-diols
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The application of clay as a catalyst for acetonide protection of N(Boc)-amino alcohols and 1,2-diols to obtain good to excellent yields of the acetonide derivatives is described. Acetonide deprotection to obtain the parent amino alcohol was carried out using a similar catalyst in the presence of methanol as solvent. The reaction takes place at room temperature within 2h to give the parent amino alcohol in quantitative yield keeping the N(Boc) group intact.
- Shaikh, Nadim S.,Bhor, Santosh S.,Gajare, Anil S.,Deshpande, Vishnu H.,Wakharkar, Radhika D.
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p. 5395 - 5398
(2007/10/03)
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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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