Biotransformation of Cycloastragenol by Cunninghamella blakesleeana NRRL 1369 Resulting in a Novel Framework

Abstract

The microbial transformation of cycloastragenol by the fungus Cunninghamella blakesleeana NRRL 1369 was investigated. Unlike the original compound, the metabolite was found to possess an interesting triterpenic skeleton derived via an exceptional transformation involving ring cleavage and methyl group migration. The structure of the new metabolite was elucidated by 1-D ((1)H, (13)C) and 2-D NMR (COSY, HMBC, HMQC, NOESY) techniques and MS analyses.

Biocatalysis of Cycloastragenol by Filamentous Fungi to Produce Unexpected Triterpenes

“…[14,19] Compound 12 possessed the molecular formula of C 30 C NMR data with those in the literature, it was identified as the known (20R,24S)-3b,6a,16b,19,25-pentahydroxy-ranunculan-9(10)-ene (spectra measured in CD 3 OD). [14] The molecular formula of compound 13 was estab- …”

“…The characteristic 9,19-cyclopropane ring of cycloastragenol were cleaved in four biotransformed metabolites (12,13,14,15) as the signals corresponding to 19-CH 2 disappeared. They were elucidated to possess the unusual ranunculane skeleton through a complicated rearrangement.…”

“…They were elucidated to possess the unusual ranunculane skeleton through a complicated rearrangement. [14] To the best of our knowledge, only two compounds with this novel skeleton had been reported so far. [14,19] Compound 12 possessed the molecular formula of C 30 C NMR data with those in the literature, it was identified as the known (20R,24S)-3b,6a,16b,19,25-pentahydroxy-ranunculan-9(10)-ene (spectra measured in CD 3 OD).…”

“…Its structural modification is thus of great necessity for further evaluation of structure-activity relationships. Recently, Kuban et al [14] reported the formation of a complicated rearrangement product of CA with a novel ranunculane framework by Cunninghamella blakesleeana NRRL 1369, which demonstrated the power of biocatalysis in structural diversification of cycloastragenol to produce novel derivatives. This paper describes the biocatalysis of cycloastragenol by three strains of filamentous fungi, namely Cunninghamella elegans AS 3.1207, Syncephalastrum racemosum AS 3.264 and Doratomyces stemonitis AS 3.1411, and structure elucidation of the 15 biotransformed products.…”

Cleavage of ring A and formation of an unusual nor-triterpene skeleton via the Baeyer–Villiger reaction

“…[10][11][12] In continuation of our studies on the chemistry and biological activities of Astragalus cycloartanes, [13][14][15][16] we have directed our efforts toward the exploration of various analogues of CA to generate a library of structurally similar compounds for cytotoxicity screening studies. Herein, we report an unusual modification of ring A of CA by utilizing the Baeyer-Villiger (BV) oxidation.…”