- Regio- and diastereoselective reduction of nonenolizable α-diketones to acyloins mediated by indium metal
-
(equation presented) α-Diketones are efficiently reduced with indium metal in methanol-water in the presence of NH4Cl, LiCl, or NaCl to give regio-and diastereoselectively the corresponding acyloins in good to excellent yield. The cleavage of the acyloins under Pb(OAc)4MeOH-PhH condition provides a convenient and regioselective access to highly functionalized cyclopentane carboxaldehydes, potential building blocks in organic syntheses.
- Khan, Faiz Ahmed,Dash, Jyotirmayee,Sahu, Nilam,Gupta, Sharad
-
-
Read Online
- Exploring the substrate specificity of Cytochrome P450cin
-
Cytochromes P450 are enzymes that catalyse the oxidation of a wide variety of compounds that range from small volatile compounds, such as monoterpenes to larger compounds like steroids. These enzymes can be modified to selectively oxidise substrates of interest, thereby making them attractive for applications in the biotechnology industry. In this study, we screened a small library of terpenes and terpenoid compounds against P450cin and two P450cin mutants, N242A and N242T, that have previously been shown to affect selectivity. Initial screening indicated that P450cin could catalyse the oxidation of most of the monoterpenes tested; however, sesquiterpenes were not substrates for this enzyme or the N242A mutant. Additionally, both P450cin mutants were found to be able to oxidise other bicyclic monoterpenes. For example, the oxidation of (R)- and (S)-camphor by N242T favoured the production of 5-endo-hydroxycamphor (65–77% of the total products, dependent on the enantiomer), which was similar to that previously observed for (R)-camphor with N242A (73%). Selectivity was also observed for both (R)- and (S)-limonene where N242A predominantly produced the cis-limonene 1,2-epoxide (80% of the products following (R)-limonene oxidation) as compared to P450cin (23% of the total products with (R)-limonene). Of the three enzymes screened, only P450cin was observed to catalyse the oxidation of the aromatic terpene p-cymene. All six possible hydroxylation products were generated from an in vivo expression system catalysing the oxidation of p-cymene and were assigned based on 1H NMR and GC-MS fragmentation patterns. Overall, these results have provided the foundation for pursuing new P450cin mutants that can selectively oxidise various monoterpenes for biocatalytic applications.
- Stok, Jeanette E.,Giang, Peter D.,Wong, Siew Hoon,De Voss, James J.
-
-
- In vivo and in vitro hydroxylation of cineole and camphor by cytochromes P450CYP101A1, CYP101B1 and N242A CYP176A1
-
Cytochromes P450 (P450s) are valuable enzymes that can generate a range of useful compounds via biocatalytic oxidations that complement traditional synthetic chemistry. In this study three bacterial P450s, P450cam (CYP101A1), CYP101B1 and the m
- Stok, Jeanette E.,Hall, Emma A.,Stone, Isobella S.J.,Noble, Margaret C.,Wong, Siew Hoon,Bell, Stephen G.,De Voss, James J.
-
-
- General and efficient α-oxygenation of carbonyl compounds by TEMPO induced by single-electron-transfer oxidation of their enolates
-
A generally applicable method for the synthesis of protected α-oxygenated carbonyl compounds is reported. It is based on the single-electron-transfer oxidation of easily generated enolates to the corresponding α-carbonyl radicals. Coupling with the stable free radical TEMPO provides α-(piperidinyloxy) ketones, esters, amides, acids or nitriles in moderate-to-excellent yields. Enolate aggregates influence the outcome of the oxygenation reactions significantly. Competitive reactions have been analyzed and conditions for their minimization are presented. Chemoselective reduction of the products led to either N-O bond cleavage to α-hydroxy carbonyl compounds or reduction of the carbonyl functionality tomonoprotected 1,2-diols or O-protected amino alcohols. The oxygenation of enolates proves to be the most general and effective methodology for the synthesis of O-protected α-oxy carbonyl compounds and nitriles A. The scope and limitations of the electron-transfer-induced radical coupling reaction with TEMPO are presented. The reaction pathways are outlined. Methods for the deprotection to α-hydroxy carbonyl compounds B are provided and discussed. Copyright
- Dinca, Emanuela,Hartmann, Philip,Smrcek, Jakub,Dix, Ina,Jones, Peter G.,Jahn, Ullrich
-
supporting information
p. 4461 - 4482
(2012/10/30)
-
- Reduction of various ketones by red algae
-
The reduction of acetophenone derivatives, (+)- and (-)-camphorquinones and steroidal ketones using red algae (Cyanidioschyzon merolae 10D and Cyanidium caldarium) was investigated. It was found that fluoro, chloro and bromo acetophenone derivatives 1a-i were reduced with good enantioselectivity. On the contrary, reduction of methyl and methoxy acetophenone 1j-o showed low enantioselectivity. The reduction followed Prelog's rule, giving the (S)-alcohols in all cases. Moreover, (+)- camphorquinone 5a was reduced to give (-)-3S- exo-hydroxycamphor 5d as the major product with high stereoselectivity in high yield. In addition, it was found that reduction of 5α-androstane-3,17-dione 8a gave the 3α-OH isomer (3α-OH/3β-OH = 76/24) with high stereoselectivity. Overall it was found that C. merolae and C. caldarium were able to reduce various substrates.
- Utsukihara, Takamitsu,Misumi, Osami,Kato, Nakahide,Kuroiwa, Tsuneyoshi,Horiuchi, C. Akira
-
p. 1179 - 1185
(2007/10/03)
-
- Photo-irradiation of α-halo carbonyl compounds: A novel synthesis of α-hydroxy- and α,α′-dihydroxyketones
-
The reaction of α-halo ketones (α-iodocycloalkanones, α-bromocycloalkanones, α-iodo-β-alkoxy esters, and α-iodoacyclicketones) with irradiation under a high-pressure mercury lamp gave the corresponding α-hydroxyketones in good yields. For α-bromoketones, it was found that α-hydroxylation does not occur. However, α-bromoketones were converted into α-hydroxyketones in the presence of KI. In the case of α,α′-diiodo ketones, α,α′-dihydroxyketones, which up to now have scarcely been reported, were obtained. This reaction affords a new, clean and convenient synthetic method for α-hydroxy- and α,α′- dihydroxyketones.
- Chai, Wen,Takeda, Akihiro,Hara, Makoto,Ji, Shun-Jun,Horiuchi, C. Akira
-
p. 2453 - 2463
(2007/10/03)
-
- A novel synthesis of α-hydroxy- and α,α′- dihydroxyketone from α-iodo and α,α′-diiodo ketone using photoirradiation
-
A novel reaction of α-iodo ketone (α-iodocycloalkanone, α-iodo-β-alkoxy ester, and α-iodoacyclicketone) with irradiation under a high-pressure mercury lamp gave the corresponding α-hydroxyketone in good yields. In the case of α,α′- diiodo ketone, α,α′-dihydroxyketone which little has been reported until now was obtained. This reaction affords a new, clean and convenient synthetic method for α-hydroxy- and α,α′- dihydroxyketone.
- Horiuchi, C. Akira,Takeda, Akinori,Chai, Wen,Ohwada, Kishoh,Ji, Shun-Jun,Takahashi, T. Tomoyoshi
-
p. 9307 - 9311
(2007/10/03)
-
- Biotransformation of (+)- and (-)-camphorquinones by plant cultured cells
-
Biotransformation of (+)- and (-)-camphorquinones with suspension plant cultured cells of Nicotiana tabacum and Catharanthus roseus was investigated. It was found that the plant cultured cells of N. tabacum and C. roseus reduce stereoselectively the carbonyl group of (+)- and (-)-camphorquinones to the corresponding α-keto alcohols.
- Chai, Wen,Hamada, Hiroki,Suhara, Jumpei,Akira Horiuchi
-
p. 669 - 673
(2007/10/03)
-
- Camphor-Derived Alcohols: An Anomalous Reaction of 3-Hydroxycamphor and the Influence of Internal Alkoxides on the Alkylation Stereochemistry of Glycinate Imines
-
Attempted imine formation between 3-hydroxycamphor and tert. butyl glycinate led to 8, the substitution product at the 3-position.Zinc-acetic acid treatment of 8 afforded 3-acetoxycamphor.Alkylation of the imine from norcamphor and tert. butyl glycinate gave no stereoselection.Alkylation of the imine from 10-hydroxymethylcamphor and tert. butyl glycinate gave stereoselectivities inferior to those obtained from the imine of camphor itself (1), but aldol condensation with benzaldehyde, a reaction not possible with 1, was effected in 71percent yield.
- McIntosh, John M.,Cassidy, Kenneth C.,Matassa, Luca C.
-
p. 5449 - 5458
(2007/10/02)
-
- Reduction by a Model of NAD(P)H. 32. Stereoselective Reduction of Camphoroquinone by a Chiral NAD(P)H Model
-
(+)-, (-)-, and racemic camphoroquinones (CQ) were reduced by each of four NAD(P)H-models such as N-(α-methylbenzyl)-1-propyl-2,4-dimethyl-1,4-dihydronicotinamide (Me2PNPH) in the presence of magnesium ion in acetonitrile with a view to elucidating the intermolecular arrangement in the transition state for asymmetric reduction.Partial rate factors for each attacking mode were calculated.Electronegative substituents in the substrate prefer to facing the carbamoyl group in Me2PNPH, which is the most important factor determining the stereochemical course of the reduction. 1-Methyl group in CQ has a tendency to interfere with the dihydropyridine moiety in Me2PNPH approaching the C2-carbonyl group in CQ.This interference is more important for the selectivity than the intrinsic exo/endo reactivity difference.
- Ohno, Atsuyoshi,Goto, Takehiko,Nakai, Jun-ichi,Oka, Shinzaburo
-
p. 3478 - 3481
(2007/10/02)
-