Pseudomonas oleovorans epoxidation

The alkane hydroxylase from Pseudomonas oleovorans is particularly suitable for the epoxidation of terminal aliphatic double bonds and enables rapid access to the (3-blocker metoprolol (Scheme 9.14) [113,116]. Complementing this regioselectivity, chloroperoxidases are particularly suitable biocatalysts for the epoxidation of (ds substituted) subterminal olefins [112,117]. This enzyme also accepts terminal olefins and is utilized for the effident synthesis of P-mevalono-ladone [118]. 

Epoxides may be formed from alkenes during degradation by Pseudomonas oleovorans, although octan-l,2-epoxide is not further transformed, and degradation of oct-l-ene takes place by co-oxidation (May and Abbott 1973 Abbott and Hou 1973). The co-hydroxylase enzyme is able to carry out either hydroxylation or epoxidation (Ruettinger et al. 1977). 

AbbottBJ, CT Hou (1973) Oxidation of 1-alkenes to 1,2-epoxides hy Pseudomonas oleovorans. ApplMicrobiol 26 86-91. 

May SW, BJ Abbott (1973) Enzymatic epoxidation. II. Comparison between the epoxidation and hydroxyl-ation reactions catalyzed by the omega-hydroxylation system of Pseudomonas oleovorans. J Biol Chem 248 1725-1730. 

It is noteworthy that, in contrast to mammalian systems, the majority of bacterial strains exhibited sufficient activity even when the cells were grown under non-optimized conditions. Since enzyme induction is still a largely empirical task, cells were grown on standard media in the absence of inducers. Furthermore, all attempts to induce epoxide hydrolase activity in Pseudomonas aeruginosa NCIMB 9571 and Pseudomonas oleovorans ATCC 29347 by growing the cells on an alkane (decane) or alkene (1-octene) as the sole carbon source failed [27]. 

Pseudomonas oleovorans contains P. oleovorans monooxygenase (POM), which is a typical co-hydroxylase for hydroxylation of the terminal methyl of alkanes as well as epoxidation of terminal olefins. The co-hydroxylation system of P. oleovorans was reconstituted from purified components, POM, rubredoxin, and a flavoprotein reductase [122], In the presence of NADH and oxygen, it oxidizes a wide range of aliphatic methyl alkyl sulfides. Enantioselectivities are very much dependent of the length of the alkyl chain of Me-S(0)-R, as exemplified by the following results ... 

May, S. W., and Abbott, B. J. 1973. Enzymatic Epoxidation. 2. Comparison between Epoxidation and Hydroxylation Reactions Catalyzed by Omega-Hydroxylation System of Pseudomonas oleovorans. J. Biol. Chem., 248,1725-1730. 

There are all sorts of problems with epoxidation by micro-organisms and in general laboratory chemists prefer to use the Sharpless or Jacobsen epoxidations described in chapter 25. The co-hydroxylase from Pseudomonas oleovorans does epoxidise aryl ethers of allylic alcohols with good selectivity and one product has been used in the synthesis of the (5-blocker metropolol.29 However the organism requires gaseous hydrocarbons as carbon sources and the epoxide products poison it. 

There are also an increasing number of non-P450 type biohydroxylases. Examples are the n-octane co-hydroxylase of Pseudomonas oleovorans and the n-decane hydroxylase of Pseudomonas denitrificans, which have been shown to be also responsible for epoxidation of 1-octene and for O-demethylation of heptyl methyl ether120 241. 

The most intensively studied microbial epoxidizing agent is the co-hydroxylase system of Pseudomonas oleovorans [1156,1157]. It consists of three protein components rubredoxin, NADH-dependent rubredoxin reductase and an co-hydroxylase (a sensitive nonheme iron protein). It catalyzes not only the hydroxylation of aliphatic C-H bonds, but also the epoxidation of alkenes [1158, 1159]. The following rules can be formulated for epoxidations using Pseudomonas oleovorans (Scheme 2.155). 

Besides Pseudomonas oleovorans numerous bacteria have been shown to epox-idize alkenes [1167, 1168]. As shown in Scheme 2.155, the optical purity of epoxides depends on the strain used, although the absolute configuration is usually R) [1169]. This concept has been recently applied to the synthesis of chiral alkyl and aryl gycidyl ethers [ 1170,1171], The latter are of interest for the preparation of enantiopure 3-substituted l-alkylamino-2-propanols, which are widely used as p-adrenergic receptor-blocking agents [1172],... 

For example, metabolic engineering and culture condition manipulation were employed to produce modified PHAs with salient features. PHAs with methyl side-chains such as PH6N (poly(3-hydroxy-6-methyl-nonanoate)) was obtained from Pseudomonas oleovorans fed with methylated alkanoic acids or in a mixture with nonanoic acid as a carbon source. PH6N crystallizes much faster than neat PHN (poly-3-hydro g nonanoate), and the melting temperature was higher (I m = 65 °C) than that of PHN [Tm = 58 Studies have shown that PHAs containing an epoxidized... 

Colbert JE, Katopodis AG, May SW. 1990. Epoxidation of cis-1,2-dideuterio-l-octene by Pseudomonas oleovorans monooxygenase proceeds without deuterium exchange. J Am Chem Soc 112 3993-3996. 

Fu H, Newcomb M, Wong CH. 1991. Pseudomonas oleovorans monooxygenase catalyzed asymmetric epoxidation of allyl alcohol derivatives and hydroxylation of a hypersensitive radical probe with the radical ring-opening rate exceeding the oxygen rebound rate. JAm Chem Soc 113 5878-5880. 

Optically active epoxides are useful chiral synthons in the phamaceutical synthesis of prostaglandins. Microbial epoxidation of olefinic compounds was first demonstrated by van der Linden [241]. Subsequently, May et al. [242] demonstrated the epoxidation of alkenes in addition to hydroxylation of alkanes by an m-hydroxylase system. Oxidation of alk-l-enes in the range C6-C12, a,(o-dienes from C6-C12, alkyl benzene, and allyl ettiers were demonstrated using an co-hydroxylase enzyme system from Pseudomonas oleovorans. i -Epoxy compounds in greater than 75% e.e. were produced by epoxidation re tions using the co-hydroxylase system [243,244]. The epoxidation system from Nocardia cor-allina is very versatile, has broad substrate specificity, and reacts with unfunctionalized aliphatic as well as aromatic olefins to produce i -epoxides [245,246]. 

Microorganisms screened for epoxidation activity were selected from bacteria belonging to the genera Rhodococcus, Mycobacterium, Nocardia and Pseudomonas. Species of Pseudomonas gave the best activities, but there were variations between the individual members, and P. oleovorans was the most active organism. The activity was further enhanced by carrying out the transformation in the presence of a cosubstrate such as glucose. 

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