Method of preparing cis-vitamin D or its derivative by solid phase photosensitizer sensitization using silica gel as carrier

Abstract

A process for preparing cis-VD or its derivatives by the photochemical method includes such steps as dissolving trans-VD or its derivatives in solvent, adding solid-phase photosensitizer composed of silica gel as carrier and photosensitive group, irradiating by (300-1000)-nm light, photosensingtization reaction, filtering, and washing to separate the resultant from photosensitizer. Its advantages are simple process and low consumption of photosensitizer.

Description

technical field [0001] The invention belongs to the field of synthesizing vitamin D and its derivatives by photochemical method, in particular to a method for preparing cis-vitamin D or its derivatives by sensitizing a solid-phase photosensitizer with silica gel as a carrier. Background technique [0002] The photoisomerization reaction of trans-vitamin D and its derivatives is an important step in the synthesis of active vitamin D. Trans-vitamin D or its derivatives are converted into cis-vitamin D or its derivatives in the presence of photosensitizers, such as active vitamin D 2 and D 3 . [0003] A large number of studies have shown that in the presence of suitable photosensitizers, trans-vitamin D or its derivatives can be converted into cis-vitamin D or its derivatives through photoisomerization reaction, and the toxic by-product tachysterol generated in the production of vitamin D Can be converted to pre-vitamin D. [0004] Organic small mo...

AI Technical Summary

Problems solved by technology

[0005] In order to improve this technology, Clarke E. Slemon (EP 0 252 740 / 1988) invented a soluble polymer photosensitizer and used it to convert the toxic by-product tachysterol generated in vitamin D production into pre-vitamin D photosensitizer. In the structure reaction, the polymer photosensitizer and the reaction substrate are dissolved in the solvent first, and the photosensitive isomerization reaction is carried out by light. After the reaction, a precipitant is added to precipitate the polymer photosensitizer, and then the sensitizer is filtered and washed. Separation from the product. Although this method omits the column chromatography separation process, the product will be included during the precipitation of the polymer photosensitizer, and some products will co-precipitate with the polymer photosensitizer. The complete separation of the sensitizer and the product requires Multiple dissolution and precipitation processes use a large amount of solvents, and the recovered mixed solvents must be purified and separated from each other before they can be reused, which brings great trouble to the actual production and application process, and some solvents form azeotropes It cannot be separated at all, resulting in a large amount of waste of solvents and serious environmental problems

Eric Goethals et al. (US 5 035 783, US 5 175217) invented another soluble polymer photosensitizer, which was used to convert the toxic by-product tachysterol generated in vitamin D production into pre-vitamin D, and trans-vitamin D is converted into cis-vitamin D in the photosensitive isomerization reaction. After the reaction is completed, the polymer photosensitizer is precipitated by changing the temperature or adding a protonic acid such as hydrochloric acid. On the one hand, this method has the problem of co-precipitation of raw materials and products with the photosensitizer. On the other hand, because vitamin D compounds are very sensitive to acids, a variety of isomerization reactions will occur under acidic conditions, and when acids are used as precipitants, more by-products will be generated in the system