Mannitol reactions

In the presence of glycerol or mannitol (polyhydroxo compounds) boric acid behaves as a much stronger acid the reaction can be represented as ... 

Etherification. The reaction of alkyl haUdes with sugar polyols in the presence of aqueous alkaline reagents generally results in partial etherification. Thus, a tetraaHyl ether is formed on reaction of D-mannitol with aHyl bromide in the presence of 20% sodium hydroxide at 75°C (124). Treatment of this partial ether with metallic sodium to form an alcoholate, followed by reaction with additional aHyl bromide, leads to hexaaHyl D-mannitol (125). Complete methylation of D-mannitol occurs, however, by the action of dimethyl sulfate and sodium hydroxide (126). A mixture of tetra- and pentabutyloxymethyl ethers of D-mannitol results from the action of butyl chloromethyl ether (127). Completely substituted trimethylsilyl derivatives of polyols, distillable in vacuo, are prepared by interaction with trim ethyl chi oro s il an e in the presence of pyridine (128). Hexavinylmannitol is obtained from D-mannitol and acetylene at 25.31 MPa (250 atm) and 160°C (129). 

Reaction of olefin oxides (epoxides) to produce poly(oxyalkylene) ether derivatives is the etherification of polyols of greatest commercial importance. Epoxides used include ethylene oxide, propylene oxide, and epichl orohydrin. The products of oxyalkylation have the same number of hydroxyl groups per mole as the starting polyol. Examples include the poly(oxypropylene) ethers of sorbitol (130) and lactitol (131), usually formed in the presence of an alkaline catalyst such as potassium hydroxide. Reaction of epichl orohydrin and isosorbide leads to the bisglycidyl ether (132). A polysubstituted carboxyethyl ether of mannitol has been obtained by the interaction of mannitol with acrylonitrile followed by hydrolysis of the intermediate cyanoethyl ether (133). 

Me2C(OMe)2, SnCl2, DME, 30 min, 54% yield. This reaction has been used to prepare the bisacetonide of mannitol on a 100-kg scale. 

We now tum our attention to the C21-C28 fragment 158. Our retrosynthetic analysis of 158 (see Scheme 42) identifies an expedient synthetic pathway that features the union of two chiral pool derived building blocks (161+162) through an Evans asymmetric aldol reaction. Aldehyde 162, the projected electrophile for the aldol reaction, can be crafted in enantiomerically pure form from commercially available 1,3,4,6-di-O-benzylidene-D-mannitol (183) (see Scheme 45). As anticipated, the two free hydroxyls in the latter substance are methylated smoothly upon exposure to several equivalents each of sodium hydride and methyl iodide. Tetraol 184 can then be revealed after hydrogenolysis of both benzylidene acetals. With four free hydroxyl groups, compound 184 could conceivably present differentiation problems nevertheless, it is possible to selectively protect the two primary hydroxyl groups in 184 in... 

Chemical Reactions. Mannitol is regenerated by treatment of the hexanitrate with Amm sulfide (Ref 6), iron in acet ac (Ref 7), ferric chloride (Ref 14), or with hydrogen iodide... 

The reaction was monitored using TLC with 5% MeOH/CH2C2 as the eluent. The desired monoacetonide 3 has a Rf = 0.25. It was desirable to run the reaction to the point where most of the higher Rf components were consumed. This will produce some unwanted L-mannitol that can be filtered off as described above. 

Maltodextrin 182 Maltose 164,165, 181-184 Mandelin s reagent 426 Manganese cations 144 Manganese(II) chloride reagent 333 Mannitol 409,410 Marking the front 132 Marmesin 67 Marquis reaction 352 Marquis reagent 299 Matacil 107... 

Another application of diastereoselective nitro-aldol reactions catalyzed by Bu4NF-3H20 is demonstrated in a simple synthesis of l,4-dideoxy-l,4-imino-D-mannitol (DIM) and amino analogues (Eq. 3.85).134 The nitro-aldol reaction of nitro compounds bearing a-oxy or a-amino function with glyceraldehyde leads to nitrohexitols, which can be reduced to the corresponding amino compounds. Cyclization gives iminopolyols, as shown in Eq. 3.85. 

A similar reaction sequence, which begins with the trisphosphitylation of mannitol (12) afforded three P-diastereomers of cyclic trithiophosphate 13 via the corresponding tricoordinated tris-chlorophosphite and amidophosphite (Scheme 5) [20],... 

An amount of 16 g. of the glycol (m. p. 18°) dissolved in 250 ml. of water was oxidized with 18 g. of silver chlorate and 0.3 g. of osmic acid. The reaction mixture yielded 3 g. of allitol and no D,L-mannitol. We may therefore assign the meso configuration to the divinylglycol melting at 18°, since on hydroxylation it yielded allitol, but not D,L-mannitol. 

Summarizing the results of many investigations, monosaccharides and such derivatives as D-mannitol and D-glucitol are rather weak acceptors. Disaccharides, including such acceptor products as isomaltose, are much better acceptors, except for certain molecules, for instance leucrose, which is not an acceptor.29,46,47 The decrease of enzyme activity with time has been described in terms of a first-order reaction. The inactivation parameters have been calculated for the immobilized enzyme. The inactivation constants kd were 0.0135 (1/d) when maltose was the acceptor (stabilizing), and 0.029 (1/d) when fructose was the acceptor.38... 

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