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Several steroidal [4,6-b,c]benzothiazepines have been prepared via base-catalyzed Michael addition of 2-aminothiophenol to 3β,17β-diacetoxyandrost-4-en-6-one. The product of this reaction has the 4β,5α stereochemistry, but cyclizes to a benzothiazepine with the steroidal 4β,5β configuration, confirmed by X-ray crystallographic analysis. 2-Aminothiophenol reacts with 3β,17β-diacetoxyandrost-4-en-6-one under acidic conditions to give a steroidal 6-spiro-benzothiazole. An androst-4-ene-3,17-dione-based [4,6]benzothiazepine has been shown to be a moderate competitive inhibitor of the human placental aromatase enzyme with IC50 = 42.3 µM. Keywords: steroid, aromatase, benzothiazepine.

A series of 3-aryl-substituted butenolides and butanolides has been prepared in a common short synthetic sequence from the corresponding aryl aldehydes. The 3-arylbutanolides are prepared by cyclisation of 3-aryl-3-cyano-1-propanols, obtained by selective reduction of 3-aryl-3-cyanopropionate esters, and are converted to 3-arylbutenolides by a sulfoxide or selenoxide elimination reaction.

Although the biocatalytic activation of carbon–hydrogen bonds by oxidation to alcohols was one of the first biotransformations to be exploited by the chemical industry, this remarkable process continues to be the subject of intense research activity. Recent developments in this area have centred on the use of new biocatalysts and substrates for C–H activation, in particular on the use of recombinant strains of yeast and bacteria expressing useful hydroxylase enzymes, on mechanistic work using hydroxylase enzymes that relies on the tools of molecular biology to address outstanding questions, particularly those of substrate selection and product predictability, and on the application of these systems for hydroxylation and heteroatom dealkylation reactions.

It has been shown previously that the vanadium bromoperoxidase from Ascophyllum nodosum mediates the production of ( R )-methyl phenyl sulfoxide with 91% enantiomeric excess from the corresponding sulfide in the presence of hydrogen peroxide. Investigation of the sulfoxidation activity of this enzyme shows that activating substituents at the para -position of the aromatic ring of methyl phenyl sulfide positively influence the selectivity of the reaction, whereas strongly electron-withdrawing groups cancel the catalyzed sulfoxidation reaction. The first evidence is presented that the vanadium bromoperoxidase catalyzes the sulfoxidation of racemic non-aromatic cyclic thioethers with high kinetic resolution.

Treatment of N-methoxycarbonyl C-carboxylate ester derivatives of L- and D-methionine and L-ethionine by chloroperoxidase–hydrogen peroxide resulted in oxidation at sulfur to produce the (RS) sulfo...

An efficient method for the preparation of multi-gram quantities of ethynyl sulfides is exemplified by the synthesis of ethynyl n.pentyl sulfide. Treatment of the latter with zirconocene chloride hydride/N-iodosuccinimide gave E-2-iodoethenyl n.pentyl sulfide in high yield and stereoselectivity. The latter compound rearranged to the Z isomer on storage at −20°C.

The biotransformation of 1,2-diphenylethane by the fungus Mortierella isabellina ATCC 42613, and that of a series of alkyl benzyl sulfides by the fungi M. isabellina and Helminthosporium species NRRL 4671 have been studied. Mortierella hydroxylates 1,2-diphenylethane in low yield, giving (S)-1,2-diphenylethanol with an enantiomeric purity of 33%. Bioconversions of deuterium-labelled and racemic 1,2-diphenylethanol by M. isabellina demonstrate that this organism performs reversible oxidation/reduction of the alcohol. Biotransformations of n-alkyl benzyl sulfides by H. species give predominantly the (S) enantiomer of sulfoxide, with no sulfone formation, but M. isabellina, although showing a general preference for the oxidation of alkyl benzyl sulfides to (R) sulfoxides, also generates sulfones from n-alkyl benzyl sulfides in a time-dependent manner that suggests a stereoselective removal of (R) sulfoxide. The latter microorganism can be used, however, for the production of (R)-benzyl methyl and benzyl isopropyl sulfoxides, and gives (S)-benzyl tert-butyl sulfoxide in low yield. Key words: biotransformation, enzymes, sulfoxides.

A series of compounds containing a cyclopropyl ring adjacent to the position of oxidation during fungal biotransformation has been prepared and subjected to enzymic oxidation using Mortierellaisabellina or Rhizopusarrhizus. Carbon hydroxylation and sulfoxidation reactions were observed, but in neither case did opening of the cyclopropyl ring occur. Both these reactions were subject to inhibition by carbon monoxide but not by cyanide ion, properties characteristic of cytochrome P-450 dependent mono-oxygenase enzymes. Hydroxylation at a cyclopropyl C—H bond has been studied by the use of phenylcyclopropane and phenylthiirane as substrates for the mono-oxygenase of M. isabellina. The former was not oxidized, but the latter was converted to phenyl glyoxylic acid in moderate yield. Keywords: biotransformation, cyclopropanes, fungi, metabolism.

The anion of 5-ethenyl-4-methyl-3-pyridinecarbonitrile 1 undergoes oxidative coupling on treatment with dibenzoyl peroxide affording 1,2-bis-(5′-ethenyl-3′-cyano-4′-pyridyl)-ethane, 2. It is also shown that the anions of 2- and 4-methylpyridine undergo oxidative coupling. In the latter case, however, the coupling reaction is accompanied by addition to the carbonyl group of dibenzoyl peroxide. The addition products have been identified as phenacyl pyridines and dipicolyl phenyl carbinols. The ethenyl side chain of 1 has been hydrated by way of the oxymercuration–reduction process and the secondary alcohol oxidized to a ketone. Both the alcohol and ketone in protected form are potentially useful intermediates in alkaloid synthesis. Keywords: oxidative coupling, 2- and 4-methylpyridines, dibenzoyl peroxide, oxymercuration–reduction.

A series of racemic substituted cyclopentanones, with alkyl groups corresponding to the upper prostanoid side chain and (or) the lower prostanoid side chain without the C-15 alcohol, has been synthesized. Using a steroid template for the prostanoid molecule as a basis for selection, fungi capable of hydroxylating steroids have been used to biotransform the prostanoid substrates. The predominant products were hydroxylated at the prostanoid C-18 and C-19 positions. The hydroxylations were enantioselective, with excesses in the range 10–60%, and in most cases the predominant configuration corresponded to that of the natural prostanoids. The stereochemistry of the C-19 hydroxyl group was found to be R by degradation of products to methyl 6-acetoxyheptanoate and comparison of that material with a resolved sample, obtained via crystallization of the brucine salt of ethyl 6-phthaloxyheptanoate. Hydroxylation at C-18 gave the S configuration of alcohol. Hydroxylation at prostanoid C-15 was observed, but in all cases this was accompanied by other reactions. Hydroxylation of Rhizopusarrhizus has been used in a preparation of (−)-15-deoxy-19-(R)-hydroxy-PGE1 and (−)-15-deoxy-18-(S)-hydroxy-PGE1. Keywords: biotransformation, hydroxylation, prostaglandins, prostanoids.

Hydroxylation of alkanenitriles (C6 to C10) and of 2-octanone, 2-nonanone and 2-decanone by Helminthosporium species NRRL 4671 occurs predominantly at the (ω-1) position to give the corresponding (R-2-alkanols in > 95% enantiomeric purity.

The formation of 2-alkanones by free and microencapsulated P. roquefortii spores in an aqueous-organic two-phase system was investigated by using substrates supplied as a solution in decane. It was shown that the spores remained catalytically active after entrapment within permeable polyamide microcapsules and readily catalyzed the formation of 2-pentanone, 2-heptanone, and 2-undecanone from short-chain alkyl esters of hexanoic, octanoic, and lauric acid, respectively, with the rate of reaction being markedly dependent on the type and concentration of the ester substrate used. In general, the optimal concentration of the esters in decane was found to be much higher than that of the respective fatty acid substrates and, in the case of alkyl dodecanoates, the biotransformation could be carried out efficiently even in the absence of added solvent. Further analysis revealed a significant difference in the reaction rates observed with free and microencapsulated spores at 0.5 but not at 3.0 M methyl dodecanoate, suggesting that at high substrate concentrations the biotransformation was no longer limited by mass transfer.

Biotransformation of a series of racemic N-benzoyl α-amino acids by the fungus Beauveria bassiana ATCC 7159 results in isolation of the corresponding D-amino acid benzamides in high enantiomeric purity and yield.

Although the biocatalytic activation of carbon–hydrogen bonds by oxidation to alcohols was one of the first biotransformations to be exploited by the chemical industry, this remarkable process continues to be the subject of intense research activity. Recent developments in this area have centred on the use of new biocatalysts and substrates for C–H activation, in particular on the use of recombinant strains of yeast and bacteria expressing useful hydroxylase enzymes, on mechanistic work using hydroxylase enzymes that relies on the tools of molecular biology to address outstanding questions, particularly those of substrate selection and product predictability, and on the application of these systems for hydroxylation and heteroatom dealkylation reactions.

An investigation of the microbial biotransformation of a range of 3 beta-, 17 beta-, and 20-acetylamino C18 to C21 steroids by microorganisms known to hydroxylate conventional steroids has been undertaken, using Aspergillus ochraceus, Bacillus megaterium, Curvularia lunata, and Rhizoputus arrhizus. A. ochraceus and B. megaterium gave products of 11 alpha- and 15 beta-hydroxylation, respectively. In the case of C. lunata, the products were predominantly those of this organism's normal C-11 beta- and C-14 alpha-hydroxylating pathways, but in one instance, 3 beta-acetylamino-7 alpha-hydroxy-5 alpha-androstan-17-one, appeared to results from direction of the site of hydroxylation by the substitution pattern of the substrate. The products from R. arrhizus generally corresponded to those previously obtained from normal steroids of similar skeleton, with 6 beta- 11 alpha-hydroxylation predominating, but again the sites of hydroxylation and the range of hydroxylated products were found to depend on the substitution pattern of the substrate.

The biotransformation of a series of corticosteroids by the fungus Penicillium decumbens ATCC 10436 has been investigated. Conversion to the corresponding 5 alpha-dihydrosteroid was observed for all the delta 4-3-ketosteroids studied with the exception of deoxycorticosterone, which was converted to a delta 1.4-diene. Deoxycorticosterone acetate was, however, converted to a 5 alpha-dihydro product concomitant with ester hydrolysis. Other substrates carrying a C-21 acetoxy group were also hydrolyzed to the alcohol. In two cases (resulting from deoxycorticosterone acetate and 11-deoxycortisone) the 5 alpha-3-keto product was further reduced to the 3 beta-alcohol. No reduction of delta 1.4-dienes was observed.

The fungus Helminthosporium species NRRL 4671 has been used for the biotransformation of a series of phenyl alkyl sulfides with alkyl groups ranging from methyl to n-hexyl, and benzyl alkyl sulfides with alkyl groups from methyl to n-nonyl. Several 2-phenylethyl and 3-phenylpropyl sulfides have also been examined as substrates, together with cyclohexyl methyl sulfide and 1- and 2-naphthyl methyl sulfides. For the majority of substrates, sulfoxide formation occurred in moderate yield and with predominant (S) chirality at sulfur; lesser amounts of sulfone product were also obtained in some cases. The data so obtained have been used to define the preparatively useful limits of S-oxidation of phenyl alkyl sulfides and benzyl alkyl sulfides by biotransformation using Helminthosporium.

1. The biotransformations of triphenyl phosphite and of triphenyl-, tri-n.-butyl-, diethylphenyl-, and ethylmethylphenyl-phosphines by the fungi Mortierella isabellina ATCC 42613, Helminthosporium species NRRL 4671, and Aspergillus foetidus ATCC 10254, have been examined. 2. The triaryl and tri-n.-butyl substrates underwent oxidation at phosphorus in low yield, a process attributed largely to auto-oxidation under the experimental conditions used. 3. The alkyl aryl phosphines were enzymically oxidized at phosphorus, but concurrent auto-oxidation also occurred. 4. Incubation of ethylmethylphenyl phosphine with M. isabellina gave the corresponding S(-) phosphine oxide in a 92% yield with an enantiomeric purity of 13%.

The effects of calcium alginate bead immobilization and the presence of organic solvents on two bioconversion reactions carried out by Mortierella isabellina ATCC 42613 have been investigated. These reactions, the 14 alpha-hydroxylation of progesterone and the sulfoxidation of thioanisole, both proceed in high yield using resting-cell bioconversions, but are not carried out by alginate bead preparations in the absence of an organic co-solvent, the best results being obtained with 5 or 10% aqueous methanol. The stereoselectivity of sulfoxidation of thioanisole was found to be dependent upon the nature and concentration of organic co-solvent.

Biocatalytic hydration of 3-methyl- or 3-ethyl-2-butenolide with resting cells of Rhodococcus rhodochrous ATCC 17895 gave the corresponding (R)-3-hydroxy-3-alkylbutanolide in moderate yield and with ≥95% e.e. © Rapid Science Ltd. 1998

The fungus Helminthosporium species NRRL 4671 oxidizes 1-isothiocyanato-4-(methylthio)butane to (−)-1-isothiocyanato-(4R)-(methylsulfinyl)butane (sulforaphane). Helminthosporium also converts 1-methylthio-4-(N-phthalimidyl)butane to the (R) sulfoxide.

(E)-3β,17β-Dihydroxyandrost-4-en-6-one oxime has been converted into (E)-6- hydroximinotestosterone and (E)-6-hydroximinoandrost-4-ene-3,17-dione by chemical methods, and into (E)-6-hydroximinoandrosta-1,4-diene-3,17-dione by biotransformation using Arthrobacter simplex ATCC 6946.

The benzylic hydroxylation of a series of para-substituted toluenes by the fungus Mortierella isabellina has been studied by using CD3, CHD2, and CH2D methyl labelled substrates. Inter- and intra-molecular primary and secondary deuterium kinetic isotope effect ratios have been determined: the intermolecular primary effects are maximal with strongly electron-withdrawing para substituents (R = CN and CF3), while the intramolecular primary effects are minimal for R = H but increase in instances where R is electron donating or withdrawing. These results are interpreted in terms of a dependence of the hydroxylation mechanism on the nature of the para substituent.

Treatment of hydrastine with p-nitrophenylchloroformate in the presence of diethylisopropylamine resulted in opening of the isoquinoline ring with the formation of an ene-lactone carbamate. The latter compound rearranged upon treatment with methanolic sodium methoxide to an indan-1,3-dione carbamate which gave, on basic hydrolysis, the corresponding amine. This was ring closed to a spirobenzylisoquinoline. In addition, acid-catalysed dehydration of the amino indandione led to the formation of two isomeric benzazepines, synthetic precursors of the rhoeadine alkaloids. The predominately formed isomer has a substitution pattern identical with that of the rhoeadines.

Re-investigation of the alkaloids of Corydalissolida yielded two further bases, ochotensine and solidaline. Spectral analysis has shown the latter to be representative of a new class of protoberberine-related isoquinoline alkaloids.

Testosterone and androst-4-ene-3,17-dione with a deuterium label in the 2α- or 2β-position have been synthesized from a common intermediate, 5α-androst-2-ene-5α,17β-diol. An improved preparation of the latter is described, together with its conversion via epoxidation, reductive epoxide opening, and subsequent oxidation and dehydration to 2β-labelled Δ4-3-oxo steroids. Treatment of the same precursor with labelled diborane leads, by a similar synthetic sequence, to both 2α- and 2β-labelled Δ4-3-oxo steroids. The stereochemical integrity of the products has been determined by high-field deuterium n.m.r.

Eight spirobenzylisoquinolines and four phthalideisoquinolines have been synthesized through 1,9-dehydrophthalideisoquinoline intermediates. The latter are reduced and rearranged in one step to spirobenzylisoquinolines of the corydaine–sibiricine type. The phthalideisoquinoline alkaloid hydrastine has been converted by invitro methods to a spirobenzylisoquinoline in two steps.

The preparation and aromatization by human placental microsomes of androst-4-ene-3-ones labelled with deuterium at C-4, C-6α, C-6β, C-16, and C-19 is described. Deuterium nmr spectra are reported for these compounds and for a sample of a 1,2-dideuterated androst-4-ene-3-one; the latter is formed nonstereospecifically by reduction of the C-1(2) double bond of a Δ1,4-diene-3-one. Aromatization by placental microsomes occurs with retention of deuterium at C-4 and C-6, but with some loss from C-16. The aromatization of 19-d1 and 19,19,19-d3 steroids in the presence of 16,16-d2 steroids has been carried out to determine the deuterium isotope effect for the oxidative removal of C-19. The values obtained (kH/kD for 19-d1 = 2.3, kH/kD for 19,19, 19-d3 = 3.2) are a combination of primary and secondary effects, but suggest that oxidation at C-19 is a rate-limiting reaction of the biosynthetic sequence.The fungus Pellicularia filamentosa NRRL 2727, reported to hydroxylate androst-4-ene-3,17-dione at C-19, gave only the products of hydroxylation at C-11α, C-11β, and C-14.

The natural abundance 13C nuclear magnetic resonance spectra of a number of isoquinoline alkaloids and related model compounds have been recorded. In almost all cases comparison of the spectra of the alkaloids with those of the model compounds has permitted unambiguous assignment of the alkaloid carbon resonances. The ability of 13C nmr spectroscopy to distinguish between diastereomeric pairs of both protoberberine and phthalideisoquinoline alkaloids has been demonstrated.

The Δ4-3-ketosteroid analog (± )-4a-methyl-4,4a,5,6,7,8-hexahydro-2(3H) naphthalenone (1) is hydroxylated at both C-8α and C-8β by Rhizopusarrhizus ATCC 11145. The ratio of C-8α to C-8β hydroxylation is compared with that obtained from the peracid oxidation of 2-ethoxy-4a-methyl-3,4,4a,5,6,7-hexahydronaphthalene (4) and a mechanism is proposed for both microbial and chemical hydroxylation in which the stereochemistry of the product is transition state controlled. The significance of this to the mechanism of microbial C-6β hydroxylation of Δ4-3-ketosteroids is discussed.

The following steroids and steroidal alkaloids have been incubated with the blight fungus Phytophthora infestans: androst-4-ene-3,17-dione, cholesterol, cholesteryl acetate, cholesteryl myristate, cholesteryl palmitate,cholesteryl stearate, dehydroisoandrosterone, 6α-hydroxy-androst-4-ene-3,17-dione, 6β-hydroxyandrost-4-ene-3,17-dione, 11α-hydroxyprogesterone, pregnenolone, progesterone, sitosterol, sitosteryl acetate, solanidine, solanine, stigmasterol, stigmasteryl acetate and testosterone. No hydroxylation was observed, but the fungus is able to oxidize alcohol functions at C-3β, C-6α, C-11β and C-17β to carbonyl. In addition, hydrolysis of acetate to hydroxyl at C-3β, and of solanine to solanidine, was observed. The relationship between metabolism and the nature of substitution at C-17β is discussed.

It is shown that 3,4-dihydroisoquinolines are activated toward nucleophilic attack by reaction with trimethylsilyl trifluoromethanesulfonate. The complex so formed reacts readily with the lithio derivative of 3-cyano-4-methyl-5-vinylpyridine, affording in a single step a tetracyclic amidine from which a lactam is obtained by hydrolysis. These reactions have been applied to the synthesis of the Alangium alkaloids, (±)-alangimaridine and alangimarine.

The mechanism of the C-21 hydroxylation of progesterone (1a) by Aspergillusniger ATCC 9142 to give 11-deoxycorticosterone (1b) has been studied by the use of progesterone derivatives and of C-21 deuterium labelled progesterones. The requirement of the C-21 hydroxylase system for a C-20 carbonyl group is demonstrated and the possibility of the involvement of this group, in the C-20,21 enol form, in the C-21 hydroxylation reaction has been discussed. However, on the basis of the observed deuterium isotope effect (KH/KD = 1.25), a mechanism for the microbial C-21 hydroxylation reaction is proposed in which the rate-determining step is the direct insertion of oxygen into a C-21 carbon–hydrogen bond and not one involving enolization of the C-20 carbonyl.In addition, C-11α and C-15β hydroxylation of both 20α- and 20β-hydroxypregn-4-ene-3-one (2a and 2b) by A. niger has been observed.

The ethylene ketal of 5,6α-epoxycholestan-3-one is converted to a ketalised Δ 4 -6α-ol on treatment with n-BuLi. However, the corresponding β epoxide undergoes opening of the ketal ring in the same reaction. Methyl- and n-butyl-lithium also react with the ethylene ketal of 3-ketocholestanes to give 3-alkyl cholestan-3-ols. The stereoselectivity of this reaction is discussed and a mechanism involving a 1,2 hydride shift is proposed.

The carbon magnetic resonance spectra of a series of C-19 hydroxy, C-5β,6β epoxy, C-5α,6α epoxy, and C-24 ethyl steroids have been assigned. Shift parameters for the C-19 hydroxyl function are listed. The data presented has led to a reassignment of the published spectra of several C5α,6 α epoxy steroids. In addition, 13Cmr spectral data for several bicyclic enones and a Δ5(10)-3-estrone are presented.

The enzymatic hydroxylations by intact fungal cells at the benzylic positions of toluene-d8, meta-fluorotoluene-α,α,α-d3, para-fluorotoluene-α,α,α-d3, ethylbenzene-α,α-d2, meta-fluoroethylbenzene-α,α-d2, and para-fluoroethylbenzene-α,α-d2 can be observed directly in an NMR tube by using 2H NMR as a probe. This technique provides a new method for the rapid screening of microorganisms for biotransformative capability. In all cases, the rate of product accumulation was uniform over a period of at least 4 days. The fluoro-substituted products were formed at a rate independent of the position of substitution, but slower than the corresponding unsubstituted substrates.

Radioactivity from [3-14C]tyrosine and from [methyl-14C]methionine is incorporated nonrandomly into predicted positions of corydaline and ochotensimine in Corydalissolida and C. ochotensis, respectively. The methyl group of methionine supplies the C-methyl group of corydaline and the exocyclic methylene group of ochotensimine, as well as the "bridge" carbon atom and the exocyclic O- and N-attached one-carbon units of each alkaloid. Maintenance of the 3H/14C ratio of [methyl-3H,14C]methionine within these units of corydaline is consistent with incorporation of intact CH3 groups.Partial loss of 3H relative to 14C is observed in the course of a Schmidt reaction of [2-3H, 2-14C] acetate.

The loss of hydrogen from the C-21 position of 5β-pregnane-3α,21-diol-20-one (tetrahydrodeoxycorticosterone, THDOC) during reductive removal of the 21-hydroxy group by the anaerobic bacterium Eubacteriumlentum has been shown to be selective for the pro-S position by the use of THDOC labelled with deuterium at the C-21 pro-S and C-21 pro-R positions. The labelled substrates were obtained by using the bacterium Clostridiumparaputrificum to reduce chemically prepared C-21 labelled samples of pregn-4-en-21-ol-3,20-dione (deoxycorticosterone, DOC) at C-3 and C-4 (5). The stereochemistry of deuterium label introduced by chemical means at C-21 of DOC was determined by comparison with a sample of 21-(R)-DOC-21-d1 produced by reduction of the corresponding aldehyde pregn-4-en-21-al-3,20-dione, 21-d by the enzyme 21-hydroxysteroid NAD oxidoreductase from beef liver. Keywords: Eubacterium, Clostridium, steroids, tetrahydrodeoxycorticosteroids.

A series of aryl substituted phenyl and benzyl methyl sulphides has been oxidized to the corresponding sulphoxides by Mortierellaisabellina NRRL 1757. The oxygen atom introduced during this enzymic oxidation is derived from the atmosphere and not from water. The rates of oxidation have been determined by uv analysis, and correlated with the Hammett p sigma constants for the phenyl methyl sulphide series. The value of ρ = −0.67 so obtained is interpreted in terms of a mechanism of oxidation at sulphur involving an electrophilic attack on the sulphide sulphur by the enzymic activated iron–oxygen complex, followed by conversion of the resulting sulphur cation to sulphoxide.

A series of C-21 substituted progesterone derivatives (R = F, Cl, Br, CH3) has been prepared, and incubated the C-21 hydroxylating fungus A. niger. No biotransformation was observed where R = Cl, Br, or CH3, but a minor amount of hydroxylation occurred at an unidentified site where R = F. Two C-11β substituted progesterone derivatives (R = F, OH) were converted to the corresponding C-11 ketone by the C-11α hydroxylator R. stolonifer, but a C-11β hydroxylator (C. lunata) was unable to perform a similar transformation with a C-11α hydroxy substrate. C. lunata hydroxylated a C-11β fluoro substrate at C-14α and C-21 in low yield. C-7α and -7β-hydroxy androst-4-ene-3,17-diones were prepared and incubated with C-7β hydroxylating (R. stolonifer) and C-7α hydroxylating (M. griseocyanus) fungi respectively. No ketone formation was observed. Similarly, the C-6β hydroxylator R. arrhizus was unable to transform a C-6α-hydroxy substrate or C-6α- or C-6β-hydroxy-B-norsteroids. No oxidation at halogen was observed for any of the substrates used. 13C–19F coupling constants for 11β-fluoroprogesterone suggest the presence of through space interactions between fluorine and both C-18 and C-19.