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一个简单、有效、低成本制备异源蛋白诱导剂IPTG(367-93-1)的新方法

 Introduction:

IPTG (isopropyl 1 -thio-β-D-galactopyranoside) is very frequently used to induce synthesis of heterologous proteins in Escherichiacoli in cases where transcription is controlled by the /ac-promoter.

The great cost of using large quantities of commercially produced IPTG has encouraged the investigation of simple and efficient methods for preparation of the compound. The aim of this work

was to design a synthetic route that can be easily used without any special knowledge in the field of carbohydrate synthesis. Thus the synthesis should be simple and economic, giving large

quantities of IPTG without any tedious purification steps.Therefore, we have developed a two-step procedure for the synthesis of IPTG, where chromatographic purification of the product can be omitted.

 

Result:

Alkyl l-thio-i3-D-galactoside syntheses are presented in the literature by various methods. The predominating strategy used is reaction of a thiol with a catalyst and an activated and suitably

protected sugar unit, e.g. acetobromogalactose (Helferich and Turk, 1956) and acetyl-protected O-(a-D-galactopyranosyl)trichloroimidate (Schmidt and Stumpp, 1983). Preparation and use

of these activated sugar derivatives demand skilful synthetic performance. An easier and more convenient way is to use a fully acetylated D-glycopyranose, which with a Lewis acid as a catalyst

and thiols, gives 1-thio-glycosides in high yields (Paulsen and Brenken. 1988). The stereoselectivity in these reactions for /3-glycosides depends mainly of a participating 2-O-acyl group in the sugar unit and performance at low temperature preventing acid-catalysed anomerization to a-glycosides.

The commercially available penta-O-acetyl-j3-D-galactopyranose and 2-propanethiol in dichloromethane were allowed to react at -40°C with stannous chloride as a Lewis catalyst.

After a reaction time of 8 h or overnight a yield >95% of crude isopropyl 2,3,4,6-tetra-o-acetyl-l-thio-β-D-galactopyranoside was obtained. Deacetylation with methanolic sodium methoxide and crystallization from dioxane gave pure IPTG in an overall yield of 88% in a synthetic scale giving 10 g. This procedure for synthesis can without any problems be scaled up by a factor of three. The synthesis can be completed in 2 days to a cost that is a small fraction of the commercial price.