Microbiological transformation of manoyl oxide derivatives by Mucor plumbeus

Remote B-Ring Oxidation of Sclareol with an Engineered P450 Facilitates Divergent Access to Complex Terpenoids

Though chiral pool synthesis is widely accepted as a powerful strategy in complex molecule synthesis, the effectiveness of the approach is intimately linked to the range of available chiral building blocks and the functional groups they possess. To date, there is still a pressing need for new remote functionalization methods that would allow the installation of useful chemical handles on these building blocks to enable a broader spectrum of synthetic manipulations. Herein, we report the engineering of a P450_BM3 variant for the regioselective C-H oxidation of sclareol at C6. The synthetic utility of the resulting product was demonstrated in a formal synthesis of ansellone B, the first total synthesis of the 2,3-seco-labdane excolide B, and a model study toward (+)-pallavicinin.

Sesquiterpene Lactones from Artemisia absinthium. Biotransformation and Rearrangement of the Insect Antifeedant 3α-hydroxypelenolide

Three new compounds, the sesquiterpenes absilactone and hansonlactone and the acetophenone derivative ajenjol, have been isolated from a cultivated variety of Artemisia absinthium. In addition, the major lactone isolated, 3α-hydroxypelenolide, was biotransformed by the fungus Mucor plumbeus affording the corresponding 1β, 10α-epoxide. A cadinane derivative was formed by an acid rearrangement produced in the culture medium, but not by the enzymatic system of the fungus. Furthermore, 3α-hydroxypelenolide showed strong antifeedant effects against Leptinotarsa decemlineata and cytotoxic activity to Sf9 insect cells, while the biotransformed compounds showed antifeedant postingestive effects against Spodoptera littoralis.

Biotransformation of an africanane sesquiterpene by the fungus Mucor plumbeus

Biotransformation of 8β-hydroxy-african-4(5)-en-3-one angelate by the fungus Mucor plumbeus afforded as main products 6α,8β-dihydroxy-african-4(5)-en-3-one 8β-angelate and 1α,8β-dihydroxy-african-4(5)-en-3-one 8β-angelate, which had been obtained, together with the substrate, from transformed root cultures of Bethencourtia hermosae. This fact shows that the enzyme system involved in these hydroxylations in both organisms, the fungus and the plant, acts with the same regio- and stereospecificity. In addition another twelve derivatives were isolated in the incubation of the substrate, which were identified as the (2'R,3'R)- and (2'S,3'S)-epoxy derivatives of the substrate and of the 6α- and 1α-hydroxy alcohols, the 8β-(2'R,3'R)- and 8β-(2'S,3'S)-epoxyangelate of 8β,15-dihydroxy-african-4(5)-en-3-one, the hydrolysis product of the substrate, and three isomers of 8β-hydroxy-african-4(5)-en-3-one 2ξ,3ξ-dihydroxy-2-methylbutanoate. The insect antifeedant effects of the pure compounds were tested against chewing and sucking insect species along with their selective cytotoxicity against insect (Sf9) and mammalian (CHO) cell lines.

Labdane-type diterpenoids from hairy root cultures of Coleus forskohlii, possible intermediates in the biosynthesis of forskolin

Significant attention has been devoted to studying hairy root cultures as a promising strategy for production of various valuable secondary metabolites. These offer many advantages, such as high growth rate, genetic stability and being hormone-free. In this study, a detailed phytochemical investigation of the secondary metabolites of Coleus forskohlii hairy root cultures was undertaken and which resulted in the isolation of 22 compounds, including four forskolin derivatives and a monoterpene. Their structures were elucidated by extensive spectroscopic analyses. These compounds could be classified into four groups viz.: labdane-type diterpenes, monoterpenes, triterpenes and phenylpropanoid dimers. Apart from one compound, all labdane type diterpenes are oxygenated at C-11 as in forskolin and a scheme showing their biosynthetic relationships is proposed.

On the biotransformation of ent-trachylobane to ent-kaur-11-ene diterpenes

The microbiological transformation of trachinodiol (1) by the fungus Mucor plumbeus afforded the corresponding 1α, 2α, 3α, and 17-hydroxy derivatives (2-4 and 6), respectively. 7β,16α,18-Trihydroxy-ent-kaur-11-ene (sicanatriol) (5) was also obtained in this feeding. The biotransformation of 1 to give 5 by this fungus may occur by enzymatic abstraction of a hydrogen atom, allylic to the cyclopropane ring, and subsequent cleavage of this ring. This route is similar to that postulated by us in plants of the genus Sideritis, where ent-trachylobane and ent-kaur-11-ene diterpenes coexist. This study confirms that hydroxylation of diterpenes by M. plumbeus occurs preferably at ring A carbons.

New Derivatives of Chromene and Acetoxyeudesmane Obtained by Microbial Transformation

Microbial transformation of dihydrobenzofuran derivative 1 and 4, 6-dihydroxy-1,5(H)-guai-9-ene (2), the major isolated compounds from Chrysothamnus viscidiflorus, afforded a new chromene derivative 3 and a new acetoxyeudesmane derivative 4, respectively. The structures of the new compounds were determined by comprehensive NMR studies, including DEPT, COSY, NOE, HMQC, HMBC and HRMS.

Biotransformations of ent-18-acetoxy-6-ketomanoyl oxides epimers at C-13 with filamentous fungi

Two ent-18-acetoxy-6-oxomanoyl oxides, epimers at C-13, have been prepared from ent-6alpha,8alpha,18-trihydroxylabda-13(16),14-diene (andalusol), isolated from Sideritis foetens, by means of several chemical pathways and a regioselective acylation with Candida cylindracea lipase (CCL). Biotransformation of these 13-epimeric ent-manoyl oxides by Fusarium moniliforme and Neurospora crassa produced mainly ent-1beta- or ent-11alpha-hydroxylations, as well as their deacetylated derivatives, in both epimers. In addition, with the 13-epi substrate N. crassa originated other minor hydroxylations by the ent-alpha face at C-1 or at C-12, whereas an ent-11beta-hydroxyl group, probably originated by reduction of an 11-oxo derivative also isolated, was achieved with the 13-normal substrate.

Microbiological transformation of two labdane diterpenes, the main constituents of Madia species, by two fungi

Microbial transformation of 13R,14R,15-trihydroxylabd-7-ene (5) and 13R,14R,15-trihydroxylabd-8(17)-ene (6) by the fungus Debaryomyces hansenii gave 1 (13R,14R,15-trihydroxy-6-oxolabd-8-ene) and 3 (7alpha,13R,14R,15-tetrahydroxy-labd-8(17)-ene), respectively. While, microbial transformation of 5 by Aspergillus niger afforded 2 (3beta,13R,14R,15-tetrahydroxy-labd-7-ene), and 13R,14R,15-trihydroxylabd-8,17-ene (6) gave 3 and 4 (3R,14R,15-3-oxotetrahydroxy-labd-7-ene). The structures of the new compounds, 1 and 2, were assigned by 1D and 2D high-field NMR spectroscopic methods. Antimicrobial activity of these compounds were tested and their MIC were determined.

The microbiological transformation of the diterpenes dehydroabietanol and teideadiol by Mucor plumbeus

The microbiological transformation of dehydroabietanol (18-hydroxy-dehydroabietane) by Mucor plumbeus led to 2alpha,18-dihydroxy-abieta-8,11,13,15-tetraene, 2alpha,15-dihydroxy-dehydroabietanol, 2alpha-hydroxy-15-methoxy-dehydroabietanol, 7beta-hydroxy-2-oxo-dehydroabietanol, 15-hydroxy-2-oxo-dehydroabietanol and 15,16-dihydroxy-2-oxo-dehydroabietanol, whilst that of teideadiol (1alpha,18-dihydroxy-dehydroabietane) gave 2alpha-hydroxy-teideadiol, 7alpha-hydroxy-teideadiol and 7beta-hydroxy-teideadiol. Thus, 2alpha- and 7beta-hydroxylation occur in both biotransformations and the 15-hydroxylation is inhibited in the biotransformation of teideadiol by the presence of a 1alpha-alcohol.

Biotransformation of the diterpenes epicandicandiol and candicandiol by Mucor plumbeus

The microbiological transformation of the diterpene epicandicandiol (1) with Mucor plumbeus gave foliol (3), sideritriol (5), and 7beta,16alpha,17,18-tetrahydroxy-ent-kaurane (7), while the incubation of candicandiol (2) gave 7alpha,9beta,18-trihydroxy-ent-kaur-16-ene (10), canditriol (11), and 7alpha,16alpha,17,18-tetrahydroxy-ent-kaurane (12). Thus, the main difference observed in both feedings, resulting from the spatial change in the orientation of the 7-hydroxyl, from axial in the substrate 1 to equatorial in 2, was the formation of a 3alpha- and a 9beta-hydroxylated derivative, respectively.

Microbial transformation of cadina-4,10(15)-dien-3-one, aromadendr-1(10)-en-9-one and methyl ursolate by Mucor plumbeus ATCC 4740

The sesquiterpenes cadina-4,10(15)-dien-3-one (1) and aromadendr-1(10)-en-9-one (squamulosone) (14) along with the triterpenoid methyl ursolate (21) were incubated with the fungus Mucor plumbeus ATCC 4740. Substrates 1, 14 and ursolic acid (20) were isolated from the plant Hyptis verticillata in large quantities. M. plumbeus hydroxylated 1 at C-12 and C-14. When the iron content of the medium was reduced, however, hydroxylation at these positions was also accompanied by epoxidation of the exocyclic double bond. In total nine new oxygenated cadinanes have been obtained. Sesquiterpene 14 was converted to the novel 2alpha,13-dihydroxy derivative along with four other metabolites. Methyl ursolate (21) was transformed to a new compound, methyl 3beta,7beta,21beta-trihydroxyursa-9(11),12-dien-28-oate (22). Two other triterpenoids, 3beta,28-dihydroxyurs-12-ene (uvaol) (23) and 3beta,28-bis(dimethylcarbamoxy)urs-12-ene (24) were not transformed by the micro-organism, however.