JULIA-COLONNA Asymmetric Epoxidation

Adger, B.M., Barkley, J V. Bergeron, S., Cappi, M.W., Elowerdew, B.E., Jackson, M. R, McCague, R., Nugent, T.C. and Roberts, S.M. Improved Procedure for Julia-Colonna Asymmetric Epoxidation of a,/l-Unsaturated Ketones Total Synthesis of Diltiazem and Taxol Side-chain. J. Chem. Soc., Perkin Trans. 1 1997, 23, 3501-3507. 

The Julia - Colonna asymmetric epoxidation of electron-deficient unsaturated ketones to the corresponding epoxides with high yields and high ee is well known. This technique produces chiral chemical entities from the clean oxidant, hydrogen peroxide, without the use of a toxic or water sensitive transition metal additive. 

J. Skidmore, and J. A. Smith, beta-Peptides as catalysts poly-beta-leudne as a catalyst for the Julia-Colonna asymmetric epoxidation of enones, Chem. Commun. 2001, (22), 2330-2331. 

D. Reichert, A. Kuhnle, H.-P. Krimmer and K. Drauz, Julia-Colonna asymmetric epoxidation in a continuously operated chemzyme membrane reactor, Synlett 2002, (5), 707-710. 

Preparation and activation of silica-supported poly-L-leucine[150] has been studied under a variety of reaction conditions leading to an efficient procedure for the preparation of material suitable for use in the Julia-Colonna asymmetric epoxidation reaction. Poly-L-leucine, can be added to the list of natural11511 and non-natural[152] oxidation catalysts that benefit from being supported on commercially available silica gel. 

Other references related to the Julia-Colonna asymmetric epoxidation are cited in the literature. 

Adger BM, Barkley JV, Bergenm S, Cappi MW, Flowerdew BE, Jackson MP, McCague R, Nugent TC, Roberts SM (1997) Improved Procedure for Julia-Colonna Asymmetric Epoxidation of a,P-Unsaturated Ketraies Total Synthesis of Diltiazem and Taxol (TM) Side-Chain. J. Chem Soc Perkin Trans I 3501... 

Cappi MW, Chen WP, Flood RW, liao YW, Rohrats SM, Skidmore J, Smith JA, Williamson NM (1998) New Proeedutes fra the Julia-Colonna Asymmetric Epoxidation Synthesis of (-t)-Clausenamide. Chtan Commun 1159... 

Chen WP, Roberts SM (1999) Julia-Colonna Asymmetric Epoxidation of Furyl Styryl Ketone as a Route to Intermediates to Naturally Occurring Styryl Lactones. J. Chem Soe Perkin Trans I 103... 

JULIA-COLONNA Asymmetric Epoxidation Asymmetric epoxidation of electron-poor olefins catalyzed by poly-a amino acids. 

An example of catalysts which are themselves heterogeneous are the poly-amino acids used for the asymmetric Julia-Colonna-type epoxidation of chalcones using alkaline hydrogen peroxide (Section 10.2) [8]. Because of the highly efficient synthesis of epoxides, this process also has attracted industrial interest (Section 14.3). Since recent work by the Berkessel group revealed that as few as five L-Leu residues are sufficient for epoxidation of chalcone, several solid-phase-bound short-chain peptides have been used, leading to enantioselectivity up to 98% ee [14], For example, (L-Leu)5 immobilized on TentaGel S NH2 , 8, was found to be a suitable solid-supported short-chain peptide catalyst for epoxidations. 

The asymmetric epoxidation of enones with polyleucine as catalyst is called the Julia-Colonna epoxidation [27]. Although the reaction was originally performed in a triphasic solvent system [27], phase-transfer catalysis [28] or nonaqueous conditions [29] were found to increase the reaction rates considerably. The reaction can be applied to dienones, thus affording vinylepoxides with high regio- and enantio-selectivity (Scheme 9.7a) [29]. 

Gerlach, A. and Geller, T. Scale-up Studies for the Asymmetric Julia-Colonna Epoxidation Reaction. Adv. Synth. Catal. 2004, 346, 1247-1249. 

In addition, solid-phase bound short-chain peptides have been recently found by the Ber-kessel group to act as highly efficient catalysts in asymmetric epoxidation reactions [17]. In the early 1980s, Julia and Colonna reported that chalcone 11 can be epoxidized asymmetrically by akaline hydrogen peroxide in the presence of poly-amino acids as catalysts [18, 19], The work by Berkessel et al. revealed that in fact as little as five I-Leu residues are sufficient for the epoxidation of the enone 11 with 96-98% ee (Scheme 8). 

Julia, S., Guixer, J., Masana, J., Rocas, J., Colonna, S., Annuziata, R. and Molinari, H. Synthetic enzymes. 2. Catalytic asymmetric epoxidation by means of polyamino-acids in a triphase system, J. Chem. Soc., Perkin Trans. 1, 1982, 1317-1324. 

Another important asymmetric epoxidation of a conjugated systems is the reaction of alkenes with polyleucine, DBU and urea H2O2, giving an epoxy-carbonyl compound with good enantioselectivity. The hydroperoxide anion epoxidation of conjugated carbonyl compounds with a polyamino acid, such as poly-L-alanine or poly-L-leucine is known as the Julia—Colonna epoxidation Epoxidation of conjugated ketones to give nonracemic epoxy-ketones was done with aq. NaOCl and a Cinchona alkaloid derivative as catalyst. A triphasic phase-transfer catalysis protocol has also been developed. p-Peptides have been used as catalysts in this reaction. ... 

A contrasting example is the peptide-catalyzed asymmetric epoxidation of chalcones, the so-called Julia-Colonna reaction. The latter authors discovered in the early 1980s that poly-amino acids such as poly-L-alanine or poly-L-leucine catalyze the asymmetric epoxidation of chalcone (37) and derivatives using alkaline dihydrogen peroxide as the terminal oxidant (Scheme 15) (49,50). 

For an overview of the Julia-Colonna epoxidation of enones, see Berkessel, A. Groger, H. Asymmetric Organocatalysis , Wiley-VCH Weinheim, 2005, Chapter 10.2. 

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