Enzymatic Dihydroxylation of Aryl Silanes - ACS Symposium Series

Chapter 27 Enzymatic Dihydroxylation of Aryl Silanes 1

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Wyatt C. Smith , Gregory M. Whited , Thomas H. Lane , Karl Sanford , and Joseph C. McAuliffe Downloaded by CORNELL UNIV on October 6, 2016 | http://pubs.acs.org Publication Date: September 19, 2008 | doi: 10.1021/bk-2008-0999.ch027

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Danisco Genencor, 925 Page Mill Road, Palo Alto, CA, 94304 Dow Corning Corporation, 2200 W. Salzburg Road, Midland, MI, 48686

Aromatic dioxygenases were used to oxidize aryl silanes to chiral (1S,2S)-3-sila-cyclohexa-3,5-diene-1,2-cis-diols with excellent stereospecificity (>95% ee). Bioconversions were conducted using a whole cell biocatalyst, E. coli JM109 expressing cloned dioxygenases, as well as by the D D T -degrading organism Ralstonia eutropha A5. Treatment of silyl cis-dihydrodiols with the enzyme cis-diol dehydrogenase gave the corresponding silyl catechols. The silane-functional cis -diols were also chemically converted into a range of derivatives by modification of the hydroxyl, silyl or olefinic functions. These silicon containing chiral cis-diols and catechols represent a novel class of compounds having potential application in the synthesis of fine chemicals, silicon -based pharmaceuticals, polymers and optical materials.

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© 2008 American Chemical Society Cheng and Gross; Polymer Biocatalysis and Biomaterials II ACS Symposium Series; American Chemical Society: Washington, DC, 2008.

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Downloaded by CORNELL UNIV on October 6, 2016 | http://pubs.acs.org Publication Date: September 19, 2008 | doi: 10.1021/bk-2008-0999.ch027

Enzymatic dioxygenation of aromatic compounds to os-dihydrodiols was first described by Gibson and coworkers in 1968, who suggested that the conversion of benzene to catechol by the microorganism Pseudomonas putida proceeded through the intermediate 3,5-cyclohexadiene ew-l,2-diol (1). The reaction was extensively studied in die following years, and has been the subject of several comprehensive reviews (2,3,4). A number of related enzymes are known to perform this transformation, including toluene dioxygenase (EC 1.14.12.11), naphthalene dioxygenase (EC 1.14.12.12), and other aromatic oxygenases, which together act upon a broad range of aromatic, heterocyclic and polycyclic substrates. Substituted aromatic compounds are converted to chiral products, depicted in Scheme 1.

OH

Dioxygenase

0, 'OH

Scheme 1. Dioxygenase-catalyzed production of a cis-dihydrodiol.

The c/s-dihydroxylation reaction catalyzed by these dioxygenases is typically highly enantioselective (often >98% ee) and, as a result, has proven particularly useful as a source of chiral synthetic intermediates (2,4). Chiral cisdihydrodiols have been made available commercially and a practical laboratory procedure for the oxidation of chlorobenzene to (IS, 2S)-3-chlorocyclohexa-3,5diene-l,2-cw diol by a mutant strain of Pseudomonas putida has been published (6). Transformation with whole cells can be achieved either by mutant strains that lack the second enzyme in the aromatic catabolic pathway, ds-dihydrodiol dehydrogenase (E.C. 1.3.1.19), or by recombinant strains expressing the cloned dioxygenase. This biocatalytic process is scalable, and has been used to synthesize polymer precursors such as 3-hydroxyphenylacetylene, an intermediate in the production of acetylene-terminated resins (7). A synthesis of polyphenylene was developed by ICI whereby the product of enzymatic benzene dioxygenation, cw-cyclohexa-3,5-diene-l,2-diol, was acetylated and polymerized as shown in Scheme 2 (8). Other industrial applications of ds-dihydrodiols have also been pursued. Merck has considered using the diol derived from indene in the production of the HIV-protease inhibitor indinavir (9). A bioprocess for indigo production was developed by Genencor where the keystep involved the dioxygenation of indole using toluene dioxygenase, summarized in Scheme 3 (10). Although microbial oxidation of a large number of substituted aromatic compounds to c/s-dihydrodiols (e/s-diols) has been previously demonstrated,

Cheng and Gross; Polymer Biocatalysis and Biomaterials II ACS Symposium Series; American Chemical Society: Washington, DC, 2008.

436

TDO

HO


AÇO

/ Γ \

//A

a

AcO

ΌΗ

OAc

Jn

Scheme 2. Polyphenylene synthesis from benzene cis-dihydrodiol

Indole

Indigo

Indole c/s-dihydrodiol

Scheme 3. Toluene dioxygenase mediates the key step in the conversion of indole to indigo in an engineered E. coli strain.

Br

SiMe 1)TDO, 0

a

C H 2

3

CH

CH

1)t-BuLi,-100°C

+

2) 2,2-DMP, H *

3

2) Me SiCI 3

3

S

C H

0

Scheme 4. Conversion ofbromobenzene into a trimethylsilyl cyclohexadiene-1,2-cis-diol acetonide.


3

3


437 there was no example in the literature of a similar transformation of an aromatic compound bearing a silicon substituent (i.e. an aryl silane) prior to our investigation (11). A previous attempt to obtain silyl-functional c/s-diols by enzymatic dioxygenation of trimethylsilylbenzene by Ley and coworkers was not successful (12), although the acetonide of trimethylsilylbenzene cis-diol was synthesized by lithiation of a bromoacetonide derived from bromobenzene, followed by addition of T M S chloride as shown in Scheme 4. We sought to examine the enzymatic dioxygenation of aryl silanes using a number of different aromatic dioxygenases in order to determine i f such transformations were possible and to define the substrate-specificity profile. We were also motivated by the rich chemistry of silicon-based materials, which includes the hydrosilylation of alkenes and ketones, the addition of electrophiles to vinyl and allyl silanes, and palladium catalyzed cross-coupling of vinyl silanes with aryl halides (13). As a result, silyl functional c/s-diols have potential as chiral intermediates for drug development, as polymer precursors/modifiers and as elements in non-linear optical materials.

Enzymatic Dioxygenation of Aryl Silanes To explore the enzymatic dioxygenation of aryl silane substrates, a small library of 26 silanes representing several structural classes was obtained from commercial sources. Compounds were selected based upon our desire to produce products that could be further elaborated to polymers, or that would contain chiral silicon atoms. Examples included silanes bearing alkoxy, vinyl and hydrido substituents, in addition to a number of diphenylsilanes. Several whole cell biocatalysts were selected for the study, summarized in Table 1. Aryl silanes were initially screened against whole cells of E. coli JM109 (pDTG601), and to some extent, S. yanoikuyae B8/36. Each aryl silane was subjected to small-scale whole cell transformation by using resuspended cells in the presence of 0.1% glucose and 1 mg/mL substrate. Substrates were typically added directly to the transformation broth and incubated for 3-4 hours before extraction with dichloromethane and subsequent analysis by thin layer chromatography (TLC), G C / M S , and *H N M R (olefinic signals in the 6-7 ppm region being diagnostic for c/s-dihydrodiol products) (11). Controls to assess the stability of the aryl silane substrate under the conditions of the transformation were run using dioxygenase-free E. coll cells (no plasmid). Since dioxygenase activity was somewhat variable, a positive control was run in parallel with every transformation experiment using the natural substrate o f the particular dioxygenase (toluene, naphthalene, or biphenyl). In most cases where products were undetectable, shake flask transformations were repeated using cells grown in a 14L fermentor, as cells grown in the fermentor under carefully controlled conditions provide cultures of extremely high cell density and enzyme activity. However, in no case was a cis-


438 Table I. A r y l dioxygenase expressing strains used to study the dioxygenation of aryl silanes. Strain E. colimm (pDTG601)

Characteristics E. coli JM109 host containing the T D O genes (IPTGinducible) \todC12BA) from Pseudomonas putida in expression plasmid pKK223-3 (Amp ) E. coli JM109 host containing the (+)-m-(/S, 2Λ)dihydroxy-3-methyleyclohexa-3,5-diene dehydrogen ase genes (todD)fromPseudomonas putida F l (IPTGinducible) in expression plasmid pKK223-3 (Amp ) E. coli JM109 host containing the N D O genes (IPTGinducible) (nahAaAbAcAd)fromPseudomonas sp9816 in plasmid pKK223-3 (Amp ) 1

E. CO//JM109 (pDTG602)


r

E CO//JM109 (pDTG141)

r

Sphingomona S. yanoikuyae strain lacking cis-à\o\ dehydrogenase syanoikuyae activity, derived from B l (wild strain) by chemical mutagenesis. Has a biphenyl-inducible biphenyl B8/36 dioxygenase (BPDO) pathway. Wild strain containing biphenyl (BP)-inducible Ralstonia eutropha A5 dioxygenases. Can utilize (BP) or 4-chlorobiphenyl as sole carbon source SOURCE: U.S.

patent 7179932.

diol product detected where there was none before. O f the enzymes tested, only toluene dioxygenase was found to accept aryl silane substrates. Complete disappearance of the substrate could sometimes be observed within 30 minutes (as determined by G C / M S analysis), but an accurate mass balance was somewhat difficult to determine due to the high vapor pressure of many of the substrates. Thus, these shake flask experiments were useful qualitative screens for dioxygenase substrates. In most cases these transformations produced relatively pure products following extraction and removal of solvents, for example the cisdiol derived from dimethylphenylvinylsilane (Figure 1). The successful bioconversions of aryl silanes to cw-diols are summarized in Table 2. The conversion of dimethylvinylsilane l a to the cw-diol 2a is noteworthy given the presence of an oxidizable vinylsilane function. Similarly, the sensitive hydrosilane function of dimethylphenylsilane l b survived both exposure to aqueous conditions, in addition to enzyme mediated oxidation. The cw-diol products listed in Table 2 were moderately stable, provided that exposure to acidic conditions was minimized, discussed in further detail later in this chapter. The product of benzyl silane (Id) dioxygenation was the exception however, with the c/s-diol (2d) undergoing a facile conversion to only the ortho-phmol at


439


2a

"j'~τ

8

1

t

τ

)-

τ

1

7

τ

1

1~—τ-™—ι——τ

6

τ

1

!

!

ι

1

5

1—— 'ι

4

5.80

ΙΛ3 1.06

~" 2.15

f

Figure 1. A 300MHz HNMR spectrum of crude dimethylphenylvinylsilane cis-dihydrodiol, obtained in d6-DMSO.

Scheme 5. Postulated mechanism for the conversion ofbenzylsilane cis-diol to an ortho-substitutedphenol through a silicon stabilized carbocation.



1c

1b

1a

Phenyltrimethylsilane

SiMe*

Dimethylphenylsilane

2

SiMe H

Dimethylphenylvinylsilane

-^^SiMeo

Aryl silane substrate

10 g scale), dimethylphenylvinylsilane (DMPVS) l a and dimethylphenylsilane (DMPS) l b .

Dimethylphenylvinylsilane (la)

Dimethylphenylsilane (lb)

The dioxygenation was performed by the addition of the neat silanes to a 14L fermentor containing E. coli JM109 (pDTG601) expressing toluene dioxygenase. The tolerance of the cells to possible toxic effects of the aryl silanes was assessed by online monitoring of the respiratory quotient (RQ), an


443 indicator of the aerobic respiration rate (18). R Q values of 0.9 or greater were maintained by adjusting the addition rate of the aryl silane substrates. The extent of conversion was monitored by either G C / M S or H N M R . Samples of whole fermentor broth (10 mL) were taken at regular intervals and extracted with 1 m L of deuterochloroform (CDC1 ). The *H N M R spectrum of the extract allowed the extent of chemical conversion to be determined. The aryl silane substrate was added to the fermentors until such time as levels of aryl silane began to increase (typically 25 to 75 g in total). At this point the fermentor broth was harvested, centrifuged to remove cells, and extracted three times with 1 L of ethyl acetate. Upon evaporation of the solvent, crude silane cisdiols 2a and 2b were obtained in yields of 40% and 64% respectively, with only minimal amounts of the aryl silane starting materials. It was important to include a bicarbonate wash of the organic extract in order to prevent the acid-catalyzed conversion to silyl phenols through dehydration. The crude cw-diols could be further purified by column chromatography over silica gel pretreated with a small amount of triethylamine. The enantiomeric excess (% ee) and absolute configuration of purified diols cw-(7S,2S)-3-(dimethylvinylsilyl)-cyclohexa-3,5diene-l,2-diol (2a) and cw-(lS,2S)-3-(dimethylsilyl)cyclohexa-3,5-diene-l,2-diol (2b) was shown to be greater than 98% ee as determined by the *Η N M R method of Resnick et al. (19). Both cw-dihydrodiols 2a and b were stable at -20°C for at least several months, although at room temperature they slowly converted to a mixture of ortho- and meta-phenols, compounds 3 a,b and 4 a,b respectively, as the result of an acid-catalyzed dehydration. !


3

3a

R

3b

R

3c

R

1

1

1

OH, R H, R R

2

2

2

= H

= OH

= OH

4a

R

4b 4c

R

1

1

= OH,R = H, R

R = R 1

2

2

2

= H

= OH

= OH

Catechol biosynthesis In organisms that are able to folly degrade toluene, the second step in the catabolic pathway involves the dehydrogenation of oy-diols to the corresponding catechols by oy-diol dehydrogenase (E.C. 1.3.1.19), as shown in Scheme 6.


444 R ΌΗ

Diol-dehydrogenase ΌΗ

OH


Scheme 6. Diol dehydrogenase mediated production of a catechol

Biocatalytic production o f catechols using E. coli (pDTG602) was demonstrated in a shake flask for c/s-diols 2a and 2b resulting in the silyl functional catechols 3c and 4c, respectively. Following extraction of the aqueous phase with ethyl acetate, the products were analyzed by G C / M S (for 3c [M ] m/z 194; 4c [M ] m/z 168) and T L C , the latter by visualization with Gibbs reagent which provides a color test diagnostic for catechols (UV-active bands turned dark brown immediately after treatment of the plate with reagent). The yield of the conversions was low however, and optimization will be needed in order to provide larger amounts of these novel compounds. +

+

Synthetic Derivatives of silyl as-dihydrodiols In order to prevent the degradation o f the somewhat labile cis-diols upon storage, they were converted to their acetonide derivatives by treatment with 2,2-dimethoxypropane (2,2-DMP) and Amberlite 120-H resin, followed by filtration and removal of solvents. Care needed to be taken in order to minimize losses of the somewhat volatile silanes during the concentration step (Table 3). +

Diels-Alder adducts of cis-diol acetonides Arene c/s-diols can undergo cycloaddition reactions, acting as both diene and dienophile to produce homoadducts (12). Heteroadducts have also been synthesized, for example recent work by Banwell and coworkers exploited the reaction of toluene cis-diol with cyclopentenone as the initial step in their synthesis of complicatic acid and related triquinanes (20). We found that upon prolonged standing at room temperature in concentrated form, the acetonides 5a and 5b were slowly converted to the Diels-Alder adducts depicted in Figure 2.

Additional derivatives Additional synthetic derivatives of the silyl c/s-diols and the corresponding acetonides were prepared in order to demonstrate the versatility o f these


445 Table III. Aeetonide derivatives of ds-diols. Aeetonide derivative


cis-diol substrate

SOURCE: U.S.

patent 7179932.



Figure 2. Diels-Alder cycloadduct dimers of dimethylphenylsilane cis-diol acetonide (5a) and dimethylvinylphenylsilane cis-diol acetonide (5b).


447 compounds. As mentioned above, dehydration to form the phenol is relatively facile (standing at room temperature, or slight acid), and so preservation of the chiral ds-diol moiety in subsequent synthetic steps is important. In addition to acetonides, the ds-diol group was protected through standard synthetic techniques including acylation, phenylboronation, or conversion to the dimethyl teri-butylsilyl ether. Further transformations of D M P S ds-diol 2b and its aeetonide derivative 5b, both by modification of the ring or simple transformation of the hydrosilane function are summarized in Schemes 7 and 8.


Epoxidation of a c/s-diol aeetonide bearing a hydrosilane functionality The chemical epoxidation of D M P S ds-dihydrodiol was performed using 2 equivalents 3-chloroperbenzoic acid (m-CPBA) in dichloromethane and gave a mixture of 4 compounds (Scheme 8). Surprisingly, the hydrosilane functionality was robust enough to allow the isolation two epoxidized products. Analysis of this mixture by H N M R gave the spectrum depicted in Figure 3. The formation of these highly functionalized, chiral silanes in just 3 steps from dimethyl-phenylsilane demonstrates the potential of this methodology. !

Naphthalene Dioxygenase Regioselectivity Naphthalene dioxygenase (NDO) is known to perform a number of other reactions in addition to cw-dihydroxylations, including monohydroxylations, desaturations, 0-and iV-dealkylations and sulfoxidations (3). In our hands, N D O was unable to convert any aryl silanes into a ds-diol product, including (1naphthyl)trimethylsilane. This lack of reactivity was thought to be related more to the steric bulk around the silicon atom, as opposed to an electronic effect. In contrast, following an incubation of 30 minutes in a shake flask with cells expressing N D O , dimethylphenylsilane (DMPS) was converted to a sole new product, identified as dimethylphenylsilanol. This was an interesting result given the fact that the analogous reaction with T D O produces only the ds-diol (2b). Figure 4 shows the results of G C / M S analysis of extracts from the two reactions. Note that the silane dy-diol derived from D M P S 2b is converted to the corresponding phenol(s) upon injection into the G C / M S . A control transformation with E. coli JM109 (no dioxygenase) cells was also run in parallel with both the N D O and T D O reactions and produced negligible amounts of dimethylphenylsilanol. In another control transformation, cumene, which can be considered the carbon analogue of D M P S , was converted completely into cumyl alcohol (1,1-dimethylbenzyl alcohol) by N D O , while T D O produces exclusively to the ds-diol Together, these results, support the hypothesis that silanol production was the result of an enzyme-mediated process.



448



Scheme 7. Derivatives of dimethylphenylsilyl cis-diol 2b.



450



Scheme 8. Derivatives of dimethylsilylphenyI cis-diol aeetonide 5b



452



Figure 3. *HNMR spectrum of a mixture ofhydrosilane-functional epoxides.


454 Si(CH ) OH 3

2

Si(CH ) H 3

V^

2

5.49 1

6.96

I

Si(GH ) H 3


II

8.02

2

OH

I. JM109(pDTG141) ( N D O ) , 0.3 g D M P S / L , 30 min. II. JM109(pDTG601) ( T D O ) , 0.3 g D M P S / L , 30 min. Figure 4. Distinct products could be detected by NDO and TDO transformations by GC/MS, corresponding to the silanol and cis-diol of DMPS respectively.

Scheme 9. Contrasting oxidation products of DMPS with TDO and NDO.

Oxidation versus Hydrolysis of Dimethylphenylsilane We were interested in determining whether the production of the silanol from D M P S was the result of a monooxidation at a silicon atom, or the result of enzyme mediated hydrolysis, as both mechanisms would give rise to the same product. In the former case, however, water would be produced, as opposed to hydrogen gas (Scheme 10). Several attempts to settle this question through 0 labeling did not result in enough of the respective products to answer this question in an unambiguous fashion, possibly due to subsequent exchange of the 0-silanol group with water. 1 8

2

18


455

+ H 0 2

Me Si 2

H

A) 0 , 2H 1 8

+

2

B) H 0 Downloaded by CORNELL UNIV on October 6, 2016 | http://pubs.acs.org Publication Date: September 19, 2008 | doi: 10.1021/bk-2008-0999.ch027

2

Me Si—OH 2

Scheme 10. Possible mechanisms for conversion of DMPS to the silanol by NDO. B) Oxidation by molecular oxygen; B) Enzyme-assisted hydrolysis of the hydrosilane function.

A r y l silanes as sole carbon source We still wished to demonstrate the stereoselective oxidation of a prochiral diphenylsilane to a product containing a stereogenic silicon atom, and thus an alternative screening approach was employed. Certain bacterial strains possess the ability to utilize aromatic compounds as the sole source of carbon and energy. Oxidative metabolism of these compounds begins with the cisdihydroxylation of the aromatic ring catalyzed by dioxygenase, followed by formation of the catechol by os-diol dehydrogenase. Ralstonia eutropha A5 is a wild type strain isolated from PCB-contaminated river sediment for its ability to use 4-chlorobiphenyl as sole carbon source (21). The organism contains a biphenyl-inducible B P D O system that was also found to degrade the environmental contaminant l,l,l,-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) (Figure 5), a substrate that no other known aromatic dioxygenase is able to transform (6). Thus, given its unusual substrate tolerance, this strain was used to screen the library of 26 aryl silane substrates, including those that were not transformed by TDO, N D O or the Sphingomonas BPO. To employ a more rapid screen, R. eutropha A5 was grown on solid M S B in the presence of each member of our aryl silane library, the appearance of colonies indicating that the organism can use that substrate as sole carbon


456


Cl

DDT

Diphenylmethylsilane

Figure 5. Comparison of the structures of DDT (1,1, l-trichloro-2,2-bis(4chlorophenyl)ethane) and diphenylmethylsilane.

source. These data are summarized in Table IV with qualitative ratings of +, ++, or +++ to indicate the extent of growth, both the rate and the density. Interestingly, many of the compounds that were not substrates for N D O or T D O are apparently utilized by A5, and growth is accompanied by a color that may indicate formation of a catechol. The fact that aryl silanes that contain two or more reactive functions at silicon (i.e. methylphenylsilane, trimethoxy-phenylsilane) are transformed by A 5 is a significant observation, since the dy-diols of these compounds would be amenable to subsequent chemical modification (i.e. polymerization). Because of its wider substrate tolerance, cloning and isolation of the A5 dioxygenase may be considered in the future.

Conclusion We have demonstrated the efficient and stereoselective enzymatic dihydroxylation of several aryl silanes to the corresponding c/s-diols. O f the aryl silanes screened, 6 of the 26 substrates were converted by toluene dioxygenase to a ds-diol product, with dimethylphenylsilane (DMPS) proving to be a particularly good substrate. In contrast to T D O , naphthalene dioxygenase (NDO) did not produce a ds-diol from any of the substrates tested, however D M P S was converted by N D O to the corresponding dimethylphenylsilanol. In addition, silyl catechols were produced upon treatment of silyl ds-diols with cells expressing the enzyme c/s-diol dehydrogenase. The silyl ds-diols could be readily converted to silyl phenols upon acid treatment, or to the stable aeetonide derivatives. Both the D M P S ds-diol and the corresponding aeetonide were converted into a range of derivatives by chemical modification of the diol, olefmic or silane functions.


457

Table IV. Growth of R. eutropha A 5 on solid MSB with various aryl silane and aromatic substrates as sole carbon source. Substrate

Growth

Biphenyl

+++

Cumene

++


Naphthalene Phenylsilane

+

Methylphenylsilane

+, brown

Dimethylphenylsilane

++, brown

Diphenylsilane

++, yellow

Diphenylmethylsilane

+++, brown

Benzyltrimethylsilane Phenyldimethylvinylsilane

+

Phenyltrimethylsilane

+

Phenyltrimethoxysilane

+++, yellow

Phenyltriethoxysilane

+++, yellow

Diphenyldifluorosilane

+

Phenylmethylsilane

++

p-Tolyltrimethylsilane

+

Chloromethyldimethylphenylsilane

+

(Dimethylphenylsilyl)acetylene Vinylphenylmethylsilane

++, brown

Phenylmethyldimethoxysilane

+

1 -Chloro-4-trimethylsilylbenzene 1.3- Divinyl-1,3-diphenyl-1,3-dimethyldisiloxane ( 1 -Naphthy 1) trimethy lsilane

+ ++, brown +

4-Iodophenyltrimethylsilane Phenylethynyltrimethylsilane Diphenyldifluorosilane

+

1.4- bis(dimethylsilyl)benzene (Dimethylphenylsilyl)methanol 1,3-Diphenyl-1,1,3,3-tetramethyldisiloxane


458 The aryl silane library was also screened for their ability to function as the sole carbon source for Ralstonia eutropha A 5 , a wild type strain expressing a biphenyl dioxygenase (BPO) enzyme. A number of silanes were observed to support growth, including diphenylsilanes and trialkoxysilanes. Overall the study indicated the feasibility of the enzymatic conversion of arylsilanes to a novel series of silane cw-dihydrodiols and catechols. Such compounds may find application as chiral polymer precursors, intermediates for natural product synthesis and other usefiil materials.


References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

Gibson, D . T.; Koch, J. R.;Kallio, R. E . Biochemistry, 1968, 7, 2653-2662. Boyd, D. R.; Sheldrake, G . N. Nat Prod. Rep., 1998, 15, 309-324. Resnick, S. M.; Lee, K . ; Gibson, D . T. J. Indust. Microbiol. 1996, 17, 348457. Hudlicky, T.; Gonzalez, D.; Gibson, D . T. Aldrichimica Acta 1999, 32, 3562. Zylstra, G . L.; Gibson, D . T. J. Biol. Chem. 1989, 264, 14940-14946. Hudlicky, T.; Stabile, M. R.; Gibson, D . T.; Whited, G . M. In Organic Syntheses, 76, 77. Williams, M . G . ; Olson, P. E., Tautvydas, K . J., Bitner, R. M., Mader, R. Α., Wackett, L . P. Appl. Microbiol. Biotechnol., 1990, 34, 316-321. Ballard, D. G . H . ; Courtis, Α.; Shirley, I. M.; Taylor, S. C. J. Chem. Soc., Chem. Commun. 1983, 954-955. Davies, I. W.; Senanayake, C. H.; Castonguay, L., Larsen, R. D., Verhoven, T. R.; Reider, P. J. Tetrahedron Lett., 1995, 36, 7619-7622. Berry, Α.; Dodge, T. C.; Pepsin, M.; Weyler, W. J. Ind. Microbiol. Biotechnol. 2002, 28, 127-133. McAuliffe, J. C.; Whited, G . M.; Smith, W.C. US patent, U S 7179932, 2007. Ley, S., Redgrave, A . J., Taylor, S. C., Ahmed, S., and Ribbons, D. Synlett, 1991, 741-742. Brook, Μ. Α., Silicon in Organic, Organometallic and Polymer Chemistry Wiley, New York, 2000. Suen, W. C.; Gibson, D. T. Gene 1994, 143, 67-71. Kim, E.; Zylstra, G . J. J. Ind. Microbiol. Biotechnol. 1999, 23, 294-302. Nadeau, L . J.; Sayler, G. S.; Spain, J. C. Arch. Microbiol. 1998, 171, 44-49. Bui, V . P.; Vidar Hansen, T.; Stenstrom, Y.; Hudlicky, T.; Ribbons, D . W . New J. Chem., 2001, 25, 116-124. Shuler M. L.; Kargi, F. Bioprocess Engineering: Basic Concepts, 2nd edn., Prentice-Hall, Upper Saddle River, 2002, p 211.


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19. Resnick, S. M.; Torok, D . S.; Gibson, D. T. J. Am. Chem. Soc. 1995, 60, 3546-3549. 20. Austin, Κ. A. B.; Banwell, M. G . ; Harfoot, G . J.; Willis, A. C. Tetrahedron Lett., 2006, 47, 7381-7384. 21. Shields, M. S.; Hooper, S. W.; Sayler, G . S. J. Bacter. 1985, 163, 882-889.


Enzymatic Dihydroxylation of Aryl Silanes - ACS Symposium Series

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