中文摘要：

目的熊果酸是存在于多种天然植物中的一种三萜类化合物，因具有广泛的生物活性而备受关注。笔者拟通过对其进行结构修饰，以增加熊果酸的结构多样性，为筛选活性更好的化合物奠定基础。方法本研究首次利用链霉菌Streptomycesgriseussubsp．griseusCGMCC4．18，通过微生物转化的方式对熊果酸进行结构修饰与改造。结果得到化学方法难以得到且微生物转化中稀有的2位羟基化产物corosolicacid（2a，3α-dihydroxy—uFS-12-en-28-oicacid）以及A环c—c单键打开的产物3，4-SeCO-ursan-4．hydroxy-12-en-3，28-dioicacid，更为可贵的是2位羟基的立体结构是Ⅱ构型，这在微生物转化中是非常少见的。转化产物的结构通过波谱数据以及报道文献得知。结论通过链霉菌Streptomycesgriseussubsp．griseusCGMCC4．18对熊果酸进行结构改造，可以有效地增加熊果酸结构的多样性，这也充分体现了微生物转化具有区域选择性强、立体选择性高的特点。

英文摘要：

OBJECTIVE To modify the structure of Ursolic acid（UA） , a pentacyclic tritet-pene acid, existing a variety of natural plants with extensive biological activities thus to increase the diversity of structure of UA and lay the foundation for screening more ac- tive compounds. METHODS The structure of UA was modified by Streptomyees griseus subsp, griseus CGMCC d. 18 by microbial transformation. RESULTS A rare hydroxylated at 2 position, product corosolic acid, 2α, 3β-dihydroxy-urs-12-en-28-oic acid which is difficult to obtain by chemical methods and the product 3,4-seco-ursan-4-hydroxy-12-en-3,28-dioic acid with cleavage of ring-A were yielded. Interesting,the hydroxylation at C-2 is ct configuration that is rare. The structures of product were established based on spec- troscopic data and reference compounds. CONCLUSION The structure diversity of ursolic acid was increased by microbial transfor- mation by Streptomyces. Furteremore, microbial transformation illustrated regional selectivity and high stereo-selectivity.