Esterification, partial selective

An increase in the duration of activity of nicotinic acid and a diminution in some of its undesirable side effects were partially achieved by esterification with selected alcohols. Upon hydrolysis by esterases the alcohol component could contribute its own therapeutic effect. Thus, acylation of the polyalcohol myoinositol, (mesoinositol) with nicotinic acid afforded the ester (V). Mesoinositol hexanicotinate (V) reduced blood cholesterol levels in the hypercholesterolemic individual but not in normal subjects [57]. In addition, patients with arteriosclerosis obliterans showed an increase in walking ability after oral therapy with mesoinositol hexanicotinate [58]. A considerable portion of the C-labeled ester (V) circulated unchanged in the blood of the cat [59]. 

The above findings show the potentials of germinating rapeseed as a cheap and easy to obfain bioca yst for complete hydrolysis of oils for me preparation of fatty acids and for partial selective hy lysis of oils or selective esterification of fatty acids for the enrichment of definite fatty acids from mixtures via kinetic resolution. 

The various tri-, di- and monoorganotin hydroxides and oxides that can be obtained by partial or complete hydrolysis of the corresponding halides or carboxylates often behave as catalysts for reactions such as esterification or transesterification, and it is partly with the aim of obtaining better and more selective catalysts that a lot of work has been carried out on these compounds in the past decade.347... 

Regioselective esterification and acetylation reactions of lactose were described by Thelwall (1982). These selective reactions produced partially protected derivatives which were of value in the further modifica-... 

Pincer-ligated iridium complexes have been used as homogeneous catalysts for the dehydrogenation of aliphatic polyalkenes to give partially unsaturated polymers. The catalyst appears to be selective for dehydrogenation in branches as compared with the backbone of the polymer.56 The mechanism shown in Scheme 1 has been suggested for an [IrCl(cod)]2-catalysed oxidative esterification reaction of aliphatic aldehydes and olefinic alcohols.57... 

Sugar esters differ from ethers by being readily hydrolyzed by alkali. Methods for the esterification of polyhydroxy compounds do not generally differ from those applicable for the esterification of simple alcohols. Primary hydroxyls may in certain cases be esterified selectively, since they are more reactive than the secondary hydroxyls. Sometimes a partial esterification of the hydroxyls is desirable. The preparation of esters is clarified by examples collected in Fig. 2-21. 

Partial sulfonation under mild conditions has been reported to improve the activity and selectivity for some processes [66-69], Thus, for the esterification of dodecanoic acid with 3-phenylpropan-l-ol in water, sulfonated polystyrene resins with low substitution degrees gave better results than those with higher loadings [69], It was suggested that conventional acidic ion exchange resins are too... 

At low water activity the rate enhancing factors apparently prevail over the rate decreasing factors, as far as the lipases from C. antarctica are concerned (see Table 1). The amount of enzyme could even be reduced by 90 % (/.e. to 4 mg) when zeolite CaA was present, for the same conversion. Surprisingly, the parallel and consecutive esterification at the 2-position was slowed down in the presence of the zeolite. The opposite is true for Rh. miehei lipase this enzyme is partially deactivated and becomes less selective at low water activity. 

By selective esterification with sulphonyl halides partially substituted sulphonate esters of sucrose can be prepared. For example, using limited quantities of toluene- -sulphonyl ( tosyl ) chloride in pyridine and subsequent purification by column chromatography, the 6,6 -ditosylate (G), 1 6,6 -tritosylate (H), and 1, ... 

Sucrose chelates in DMSO react selectively with allyl halide and sodium bromoacetate to produce monoethers in high yields. Sucrose chelates in DMF solution react selectively with acid chlorides, cuihydrides and esters to produce sucrose monoesters or, in some cases, diesters as well. The yields and selectivities of the partial esterification of sucrose via chelates is higher than with other methods. The yield range of the acid derivatives studied are shown in Table XI. 

The benzylidene config. appears to be (i -) as illus., but this does not appear to be explicit in the lit. Cryst. (EtOH aq.). Mp 198-199°. [a]n -67.4 (c, 0.98 in CHCI3). The 2-OH and 3-OH groups show little selectivity in partial etherification or esterification reactions, unlike Methyl 4,6-0-benzylidene-a-D-glucopyrano-side, M-164. 

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