Klaus Kieslich

Microbial transformations of terpenoids with 1-p-menthene skeleton

SummaryMonoterpenoids with 1-p-menthene-structure can be transformed by Corynespora cassiicola DSM 62 474, DSM 62 475, and Diplodia gossypina ATCC 10 936 to chiral 1,2-trans-diols in yields of more than 60% with only minor amounts of side-products. Whereas the substrates (S)-(-)-limonene, α-terpinene, γ-terpinene, and terpinolene are converted to the (1R,2R)-p-menthene-1,2-diols, (R)-(+)-limonene and (R)-(-)-phellandrene yield the (1S,2S)-1,2-diols. For the transformation of (S)-α-terpineol and (S)-α-terpinene-4-ol to the (1S,2S)-1,2-diols Gibberella cyanea DSM 62 719 can be used, which however oxidizes parallel at the 6- and 7-position.

Synthesis of galanthamine and related alkaloids - new approaches. I.

Abstract Modifications of protecting groups and of the oxidative coupling conditions lead to pure crystalline intermediates in the synthesis of galanthamine derivatives and gave dienone A in better yields than reported before. The E -configuration of amide 3′ in crystalline state has been determined by X-ray diffraction. Streptomyces affinis 6737 reduces A to the optically active (−)-epigalanthamine derivative C, whose absolute configuration was determined by Bijvoets method. Nematospora corylii CBS 2608 reduces to racemic B. With Ashbya gossypii IFO 1355 a mixture of racemic B and optically active C is obtained. some other microbial transformations are described.

Microbial oxidation of tricyclic sesquiterpenoids containing a dimethylcyclopropane ring

Abstract Calarene was oxidized by Bacillus megaterium and Diplodia gossypina to give allylic calarenols and calarendiols in which either of the geminal methyl groups of the cyclopropane ring was hydroxylated. Globulol was hydroxylated faster and in higher yields than calarene by both strains. In the case of this compound, vicinal diols were formed and, again, either of the geminal methyl groups was oxidized. Only bacterial strains caused 9-hydroxylation. Mycobacterium smegmatis produced globulol-14-exo-14-oic acid in good yields. Of the geminal methyl groups, the one in the exo-orientation was attacked preferentially by all of the strains tested. Some of the metabolites formed are stereoisomers of known natural products.

Microbial ωoxylation of trans-Nerolidol and Structurally Related Sesquiterpenoids

Trans-nerolidol and other related terpenoid compounds varying in configuration and chain length, cis-nerolidol, farnesol, and nerylacetone, were used as substrates in biotransformation reactions. These transformations afforded, among the various metabolites obtained, at least one ω-hydroxylated compound of each respective terpenoid. Aspergillus niger ATCC 9142 and Rhodococcus rubropertinctus DSM 43197, incubated with trans-nerolidol, both gave the 12-hydroxy-trans-nerolidol and the latter, in addition, was further oxidized to the 12-carboxylic acid of trans-nerolidol in fairly good yield.

Oxidation of carenes to chaminic acids by Mycobacterium smegmatis DSM 43061

Summary(+)-2-Carene is oxidized to (−)-isochaminic acid by Mycobacterium smegmatis DSM 43061. The side product (+)-2-carene-4-one is formed partially by autoxidation. (+)-3-Carene yields, under the same conditions, (+)-chaminic acid together with (+)-3-carene-5-one and a compound with a cleaved cyclopropane ring, 2-(3′-methylcyclohexa-3′,5′-dienyl)propane-2-ol.

Regioselectivity of the microbial hydroxylation of nortricyclanol and its derivatives

While biotransformations of nortricyclanol did not give detectable products, microbial hydroxylation could be achieved by using its benzoate ester or its phenylcarbamate. Here eight fungi were found to hydroxylate these substrates in moderate yield. All strains formed optically active exo, endo-5-hydroxy-nortricyclanol-3-benzoate or -phenylcarbamate as the main product. Rhizopus arrhizus ATCC 11145 and Mortierella isabellina DSM 63355 were the best strains. Only the fermentation of the benzoate gave additional products, namely the corresponding endo, exo- and exo, endo-isomers in low yield. The structures of the metabolites were elucidated spectroscopically, particularly by using various NMR techniques. The hydroxylated nortricyclanol esters are compounds which are difficult to produce chemically. The presence of the ester function makes them chiral compounds and the biotransformations were found to be enantioselective. Therefore, microbial oxidation of these nortricyclanol esters is a valuable tool to produce chiral hydroxylated nortricyclanol derivatives which can serve as intermediates in syntheses.

Biotransformation of tetramethyl-limonene

SummaryMicroorganisms which efficiently oxidize limonene 1, do not attack 3,3,5,5-tetramethyllimonene 4. Gibberella cyanea which converts limonene 1 into 8-p-menthene-1,2-diol 2, transforms 4 into 8,9-epoxy-3,3,5,5-tetramethyl-1-menthenol-6 5 as major product. Although epoxidation is not completely stereoselective, the substituents at C-4 and C-6 are always trans to each other.

Acyloin condensation of acyclic unsaturated aldehydes byMucor species

Summary2E,6Z-Nonadienal, 2E,4E-nonadienal, citral and geraniol as precursors of geranial from acyloins enzymatically by reaction with activated acetate during fermentation by Mucor circinelloides CBS 39 468. The acyloins were reduced immediately by the fungus to (2S,3R)-diols. Reduction of the aldehyde group, including hydrogenation of the conjugated C-C double bond, hydroxylation of these alcohols and of the formed diols and some cyclizations are found as side reactions.

Microbial Hydroxylation of Cedrol and Cedrene

Abstract Biotransformation of cedrol with 5 different strains afforded 8 previously undescribed hydroxy-cedrols. The attack came from a hemisphere centered at C-12 approximately. At two positions epimeric pairs were formed, which could be avoided by using different strains. Contrary to previous studies of other groups we found the 2-and 12-hydroxylations as main reactions. Cedrene needed prolonged fermentation and gave lower yields than cedrol. Apart from allylic hydroxylations the oxidation pattern by Corynespora cassiicola DSM 62474 of cedrene and cedrol was the same. The structures of the metabolites were elucidated by 2D NMR techniques.

MICROBIOLOGICAL HYDROXYLATION AND N- OXIDATION OF CINCHONA ALKALOIDS

Biotransformations of several structurally related cinchona alkaloids were investigated, mimicking mammalian metabolism. Quinine was oxidized to the 1-N-oxide and 1′-N-oxide by Microsporum gypseum, whereas Cunninghamella echinulata yielded the known 3-hydroxy-quinine. Xylaria digitata and Mycobacterium smegmatis oxidized the 1-N of quinidine whereas Mycobacterium gypseum formed the 1-N-oxide of hydroquinidine. No microorganism was found to attack cinchonine. The 1-N-oxide of cinchonidine was obtained with Pellicularia filamentosa. The so far unknown 3-hydroxy-cinchonidine was formed by Rhizopus arrhizus ATTC 10260 and ATCC 11145. As the metabolites could be isolated in yields of up to 9%, these biotransformations offer a method for preparative use.