Mannitol formation processes

Sugihara and Schmidt49 reported the isolation of 2,5-anhydro-D-glucitol in crystalline form its preparation on a relatively large scale has been described in the patent literature,50 and consists in the thermal dehydration of D-mannitol. The process leads to the formation of 1,4-anhydro-D-mannitol, 1,5-anhydro-D-mannitol, 1,4 3,6-dianhydro-D-mannitol, and 2,5-anhydro-D-glucitol, which is isolated as the crystalline 1,3-O-isopropyIidene derivative (35). 

An interesting feature of the synthesis is the use of allyl as a two-carbon extension unit. This has been used in the stereospecific synthesis of dicyclohexano-18-crown-6 (see Eq. 3.13) and by Cram for formation of an aldehyde unit (see Eq. 3.55). In the present case, mannitol bis-acetonide was converted into its allyl ether which was ozonized (reductive workup) to afford the bis-ethyleneoxy derivative. The latter two groups were tosylated and the derivative was allowed to react with its precursor to afford the chiral crown. The entire process is shown below in Eq. (3.59). 

The bis(dioxolanyl)oxazolidinone 33 has been prepared from D-mannitol and evaluated as a chiral auxiliary <02MT749> and the diamine 34 has been examined as a ligand for rhodium catalysed asymmetric hydrogenation of diethyl itaconate <02JOU104>. Deracemisation of 2-benzylcyclohexanone by formation of an inclusion complex with the TADDOL compound 35 has been described and the mechanism clarified by X-ray structure determination of the complex <02T3401>. A production process for the bis(phosphine oxide) 36 has been patented <02USP6472539>. 

Veksler et al found that to accomplish selective hydrogenation of D-fiaictose to the preferential formation of mannitol, the pH of the modifying solution of TA is important. This process was studied using RNi modified with (2S,3S)-TA > L-Glu > (2i ,3i )-TA > RNi RNi-(55)-Tart proved to be the best catalyst among the other modified catalysts. Hydrogenation of an... 

Polyols are esterified directly with fatty acids of edible fats in such a way that formation of anhydro-polyols are minimized. The reaction is carried out at a relatively low temperature of about 150°C with sodium soaps of the fatty acids as catalysts. Exeum-ples of the esters made by this process include sorbitol, mannitol, lactitol and other polyols. Additional derivatives are made by further esterification with organic acids such as citric and diacetyltartaric acid. The polyol esters exhibit a surfactant character equivalent to the sucrose esters and find uses in similar applications. 

As seen in Fig. 4.30, the relative humidity has a strong influence on the drying process of mannitol. With increasing relative humidity, the point of the solid layer formation (solid arrow) is delayed and the normalized surface of the dried particle (dotted arrow) decreased. 

The formation of the observed particle shapes can be explained by the drying process of bicomponent mannitol-water droplets as illustrated in Fig. 14.10. The drying starts with the evaporation of water from the droplet surface (Fig. 14.11 ). The temperature of the shrinking particle rises to reach a plateau at the wet bulb temperature. Next, the solubility of mannitol is reached at the droplet surface, so that shell formation starts aU over the surface of the droplet simultaneously (Fig. 14.11(D) [54]. The inner temperature starts to increase again since evaporation of water is hindered due to the shell. Consequently, the inner pressure rises (Fig. 14.11(3))- On the one hand, this creates a stabilising effect on the spherical... 

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