Preparation Of Valienamine From Validamycins、Acarbose And Its Derivatives

Valienamine is an unsaturated aminocyclitol compound. The absolute configuration of valienamine is similar to that of a-D-glucose, and it demonstrates strong inhibitory activity against glucosidase. As the key moiety of variousα-glucosidase inhibitors, valienamine can be used as a chemical intermediate in the synthesis of other strong aglycoside inhibitors, such as acarbose and voglibose, which are most widely used drugs for type II diabetes mellitus at present due to their strong ability to delay the absorption of carbohydrates by competitive inhibition of intestinalα-glucosidases.Both of Acarbose and validamycin A have a valienamine moiety in their structure s. Besides chemical synthesis, valienamine is mainly produced by cleavage of Acarbose, which is effective but costly, or by degradation of validamycin A, which has a low efficiency and produces impurities. In this paper, the methods for preparation of valienamine by acarbose and validamycin A are completely discussed in details. A new method——capillary electrophoresis is also established for the analysis of valienamine, acarbose and validamycins, which makes a great progress in analysis efficiency.It was found in this research that no valienamine was produced after reaction of validamycin A with acid, base or ion exchange resin. Although acarbose could react with trifluoroacetic acid or ion exchange resin to produce valienamine, the yield is very low.However, the highest yield of valienamine was finally obtained through the reaction of acarbose with sodium hydroxide for about 30min at 121℃. The most desirable ratio between acarbose and sodium hydroxide is 1 to 4, and the highest valienamine yield could reach 84.2%. Valienamine could also be obtained with the same efficiency of transformation as acarbose when an acarbose derivative, component C in the fermentation broth, was reacted with sodium hydroxide.Four strains with the ability to convert validamycins to valienamine were isolated from the laboratory collection of strains, in which strain SIPI-V08 has the highest efficiency of transformation. The transformation efficiency of strain SIPI-V01 and SIPI-V29 are lower, and strain SIPI-V23 the lowest. The yiled of valienamine was obviously improved through optimization of fermentation medium and condition. The relationship between resting cells cultivation and transformation efficiency was also studied, but the result did not turn out to be satisfactory.The conversion of validamycin A to valienamine was completed via three steps of enzymatic catalytic reactions involved in several different enzymes. When different strains were co-incubated, the total yield of valienamine could be greatly improved by complementary effect resulting from the interaction of various enzymes in them. Thus, mixed transformations of four strains were studied, and some combinations of the strains resulted in great increase in total yield. The best result comes from the mixed transformation of strain SIPI-V08-V23、SIPI-V01-V08、SIPI-V01-V08-V23. On the other hand, the inhibition of transformation by high concentration of substrate could be strongly attenuated with mixed transformation. Even if the substrate concentration is up to 10%, the transformation could be efficiently performed. The mixed transformation at 10% substrate concentration by resting cells cultivation was also studied and the yield was significantly improved. Meanwhile the total cultivation time was half-shortened as well. The valienamine yield by mixed transformation of strain SIPI-V08-V23、SIPI-V01-V08 or SIPI-V01-V08-V23 exceeded 5.0mg/ml on the 3rd day, however, it required 6 days for strain SIPI-V08 alone to reach the same yield. Valienamine yield by strain SIPI-V08-V23 could reach the maximum 10.4mg/ml on the 7th day and the yield by strain SIPI-V01-V08 could reach the maximum 9.2mg/ml on the 5th day.