Method for photosensitized isomerization of tachysterol and its derivs. into previtamin D and its derivs. using cross-linked polymer photosensitier

Abstract

The invention belongs to the field of synthesizing vitamin D by photochemical methods, in particular to a method for photoisomerizing tachysterol and its derivatives into pre-vitamin D and its derivatives by using a cross-linked polymer photosensitizer. Dissolving tachysterol or its derivatives in a solvent, in the presence of a cross-linked polymer photosensitizer, wherein the molar ratio of the photosensitive group in the cross-linked polymer photosensitizer to the reaction substrate tachysterol or its derivatives is 1: 100 to 1000:1, irradiated with light of about 300nm to 1000nm to carry out sensitization reaction to obtain previtamin D or its derivatives. The polymer skeleton can be various types of polymers. Cross-linking makes these polymers insoluble in various solvents. After the sensitization reaction, these polymer photosensitizers can be easily removed from the reaction system by filtering and washing.

Description

technical field [0001] The invention belongs to the field of synthesizing vitamin D by photochemical methods, in particular to a method for photoisomerizing tachysterol and its derivatives into pre-vitamin D and its derivatives by using a cross-linked polymer photosensitizer. Background technique [0002] Tachysterol and its derivatives are toxic by-products generated during photochemical synthesis of vitamin D and its derivatives. In the presence of photosensitizers, tachysterol or its derivatives can be converted into pre-vitamin D or its derivatives through photosensitive isomerization. The resulting pre-vitamin D or its derivatives can be easily converted into vitamin D or its derivatives by heating, such as vitamin D 2 、D 3 . The photoisomerization reaction of tachysterol is an important reaction for high-yield synthesis of vitamin D. [0003] A large number of studies have shown that in the presence of suitable photosensitizers, trans-vitam...

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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 photoconstitution reaction, the polymer photosensitizer and the reaction substrate tachysterol are first dissolved in the solvent, 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 photosensitizer is filtered and washed. 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 photosensitizer 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 5175 217) 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 The photosensitizer is transformed into cis-vitamin D. 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, 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