10334-13-1Relevant articles and documents
Molecular cloning and functional characterization of a two highly stereoselective borneol dehydrogenases from Salvia officinalis L
Drienovská, Ivana,Kolanovi?, Dajana,Chánique, Andrea,Sieber, Volker,Hofer, Michael,Kourist, Robert
, (2020)
Enzymes for selective terpene functionalization are of particular importance for industrial applications. Pure enantiomers of borneol and isoborneol are fragrant constituents of several essential oils and find frequent application in cosmetics and therapy. Racemic borneol can be easily obtained from racemic camphor, which in turn is readily available from industrial side-streams. Enantioselective biocatalysts for the selective conversion of borneol and isoborneol stereoisomers would be therefore highly desirable for their catalytic separation under mild reaction conditions. Although several borneol dehydrogenases from plants and bacteria have been reported, none show sufficient stereoselectivity. Despite Croteau et al. describing sage leaves to specifically oxidize one borneol enantiomer in the late 70s, no specific enzymes have been characterized. We expected that one or several alcohol dehydrogenases encoded in the recently elucidated genome of Salvia officinalis L. would, therefore, be stereoselective. This study thus reports the recombinant expression in E. coli and characterization of two enantiospecific enzymes from the Salvia officinalis L. genome, SoBDH1 and SoBDH2, and their comparison to other known ADHs. Both enzymes produce preferentially (+)-camphor from racemic borneol, but (?)-camphor from racemic isoborneol.
DISSOLVING METAL REDUCTIONS OF KETONES: COMMENTS ON THE DIANION MECHANISM
Huffman, John W.,Liao, Wen-Pang,Wallace, Richard H.
, p. 3315 - 3318 (1987)
The reduction of (+)-camphor using Li, Na, and K in THF with sonication is reported.These reductions give the same results as those obtained in NH3.The mechanism of these reactions is discussed.
Chiral β- and γ-aminoalcohols derived from (+)-camphor and (-)-fenchone as catalysts for the enantioselective addition of diethylzinc to benzaldehyde
Dimitrov, Vladimir,Dobrikov, Georgi,Genov, Miroslav
, p. 1323 - 1329 (2001)
The addition of Me3SiCN and LiCH2CN to (+)-camphor and (-)-fenchone, respectively, followed by reduction leads to chiral β- and γ-aminoalcohols. The enantioselectivities realized using these aminoalcohols as ligands in the addition of Et2Zn to benzaldehyde were lower than those obtained using the corresponding δ-aminoalcohols.
Treating the camphors with potassium in liquid ammonia leads to a double Horeau duplication
Rautenstrauch, Valentin,Mégard, Patrick,Bourdin, Bernadette,Furrer, Anton
, p. 1418 - 1428 (1992)
When potassium dissolves in solutions of the enantiomeric camphors R-1 and S-1, variously enantioenriched camphors (1), and racemic camphor RS-1 in liquid ammonia/THF at -77°C, potassium alcoholates of the borneols R-2 and S-2 and isoborrieols R-3 and S-3 plus equivalent amounts of the potassium enolates of R-1 and S-1 - enantiomeric, enantioenriched, and racemic - are produced by a transfer of a β-hydrogen from some 1-derived unit to another [a ketyl disproportionate (hydrogen atom transfer)?]; the exact mechanism is still unknown. Hydrolysis gives enantiomeric, racemic, and enantioenriched 1-3. The mole fractions and enantiomeric compositions (ec's) of 2 and 3 were determined and plotted against the ec's of the substrates 1. The extremes of the resulting three curves are defined by the enantiomers R-1 and S-1 leading to about 1/1 mixtures of R-2 and R-3 and S-2 and S-3, respectively, and the turning points by RS-1 leading to a 9/1 mixture of RS-2 and RS-3. The ec vs ec curve is close to linear in the case of 2 and strongly nonlinear in the case of 3: from enantioenriched substrates 1, one obtains isoborneols 3 with ec's that are strongly amplified with respect to the ec's of the substrates. Fitting the plots into a statistical kinetic model suggests (1) that 3 is formed via one homochiral process (involving units with the same chirality) and 2 via a combination of second homochiral process with a single heterochiral one (involving units with opposite chirality), (2) that the rate-determining steps in these processes are fourth order with respect to the substrates 1 (!), and (3) that all parallel steps have similar or identical rate constants. The homochiral process that leads to 3 amounts to a double Horeau duplication. Statistical oligomerization or condensation of enantioenriched monomers to short oligomers leads to homochiral oligomers with strongly amplified ec. (+)-Camphor R-1 (ec 99.6%) and (-)-camphor S-1 (ec 98.3%) from the chiral pool were not quite enantiopure.
Synthesis of a new thiocarbamate by the reaction of benzyl thiocyanate with camphene, catalyzed by heteropoly acids
Arkhipova,Malkova,Sokolova,Kartashov
, p. 162 - 163 (2007)
The reaction of benzyl thiocyanate with camphene in the presence of heteropoly acids, 12-phosphotungstic and 12-silicotungstic, at 65 C was studied. S-Benzyl (1,7,7-trimethylnorbornyl)thiocarbamate was prepared in 66% yield.
Selective ruthenium-catalyzed epimerization of chiral sec-alcohols
L?ngvik, Otto,Mavrynsky, Denys,Leino, Reko
, p. 255 - 259 (2015)
Extension of secondary alcohol racemization catalyzed by homogeneous half-sandwich ruthenium complexes to the epimerization of natural products containing additional non-functionalized stereo-centers has been investigated. Ruthenium-catalysed epimerization of the sec-alcohols (-)-menthol, (-)-isopulegol, (+)-borneol, (+)-fenchol and cholesterol under mild reaction conditions and low catalyst loadings (2 mol%) provides rapid access to their less abundant diastereoisomers (+)-neomenthol, (+)-neoisopulegol, isoborneol, beta-fenchol and epicholesterol in admixture with the parent diastereomers in ratios ranging from 1:4.9 to 1:2.4 (epimer:parent).
Copper(II) exchanged cation exchange resin: Useful activator in the reduction of ketones
Sarkar,Rao,Ram
, p. 291 - 296 (1993)
A copper(II) exchanged cation exchange resin has been used as support for reduction of ketones with sodium borohydride. Supported Cu(II) ions activate the reduction of ketones to a large extent and control the stereochemistry of reductions of cyclic ketones resulting in preponderance of equatorial alcohol in most cases.
Chiral synthesis via organoboranes. 43. Selective reductions. 58. Reagent-controlled diastereoselective reduction of (+)- and (-)-α-chiral ketones with (+)- and (-)-B-chlorodiisopinocampheylborane
Ramachandran, P. Veeraraghavan,Chen, Guang-Ming,Brown, Herbert C.
, p. 95 - 99 (1996)
Asymmetric reduction of (+)- and (-)-α-chiral ketones with (+)- and (-)-B-chlorodiisopinocampheylborane provides the product alcohols in very high diastereomeric excess, with the matched pairs providing > 100:1 selectivity and the mismatched pairs showing 4:1-15:1 selectivity. The high selectivity achieved even in the mismatched pairs reveals the power of the reagent to control the stereochemical outcome. The rates of the reaction of the matched pairs are faster than those of the mismatched pairs. In all the cases studied thus far, the (-)-reagent (dIpc2BCl) and (S)-ketone or the (+)-reagent (lIpc2BCl) and (R)-ketone constitute matched pairs and the (-)-reagent and (R)-ketone or the (+)-reagent and (S)-ketone constitute mismatched pairs. A possible mechanism for the reductions is discussed.
Reliable HPLC separation, vibrational circular dichroism spectra, and absolute configurations of isoborneol enantiomers
Gao, Rui-Qi,Fan, Jun,Tan, Qi,Guo, Dong,Chen, Tao,He, Ru-Jian,Li, Dan,Zhang, Hui,Zhang, Wei-Guang
, p. 550 - 557 (2017)
Resolution of chiral compounds has played an important role in the pharmaceutical field, involving detailed studies of pharmacokinetics, physiological, toxicological, and metabolic activities of enantiomers. Herein, a reliable method by high-performance liquid chromatography (HPLC) coupled with an optical rotation detector was developed to separate isoborneol enantiomers. A cellulose tris(3, 5-dimethylphenylcarbamate)-coated chiral stationary phase showed the best separation performance for isoborneol enantiomers in the normal phase among four polysaccharide chiral packings. The effects of alcoholic modifiers and column temperature were studied in detail. Resolution of the isoborneol racemate displayed a downward trend along with an increase in the content of ethanol and column temperature, indicating that less ethanol in the mobile phase and lower temperature were favorable to this process. Moreover, two isoborneol enantiomers were obtained via a semipreparative chiral HPLC technique under optimum conditions, and further characterized by analytical HPLC, and experimental and calculated vibrational circular dichroism (VCD) spectroscopy, respectively. The solution VCD spectrum of the first-eluted component was consistent with the Density Functional Theory (DFT) calculated pattern based on the SSS configuration, indicating that this enantiomer should be (1S, 2S, 4S)-(+)-isoborneol. Briefly, these results have provided reliable information to establish a method for analysis, preparative separation, and absolute configuration of chiral compounds without typical chromophoric groups.
A NEW CLASS OF STEREOSELECTIVE REDUCING AGENTS, POTASSIUM 9-ALKYL-9-BORATABICYCLONONANES
Cha, Jin Soon,Yoon, Mal Sook,Kim, Young Shick,Lee, Kwang Woo
, p. 1069 - 1070 (1988)
A new class of reducing agents, potassium 9-alkyl-9-boratabicyclononanes (K 9-R-9-BBNHs) was examined its stereoselectivity toward cyclic ketones.Among these, K 9-TB-9-BBNH reveals the most favorable stereoselectivity, comparable to that by lithium trisiamylborohydride at 0 deg C.
