1,2-Propanediol 5, 1-chloro-2-propanol 8 and its related 2-O-acetate 9 were partially resolved by chemoenzymatic acetylation and deacetylation, in the presence of Pseudomonas fluorescens lipase (Amano P.; PFL), to (R)-(−)-1-acetoxy-2-propanol 6, (R)-(+)-2-acetoxy-1-chloropropane 9 and (R)-(−)-1-chloro-2-propanol 8, respectively. On the other hand, treatment of (2RS)-2 with vinyl acetate in ether and Chirazyme® L-2 gave 2-O-acetyl-1,3,4-trideoxy-5,6:7,8-di-O-isopropylidene-β-d-manno-non-5-ulo-5,9-pyranose 1 and 1,3,4-trideoxy-5,6:7,8-di-O-isopropylidene-β-d-gluco-non-5-ulo-5,9-pyranose 11, respectively. Compound 10 was subsequently deacylated to 12. Both alcohols 11 and 12 were treated with Me2CO/H+ to cause their rearrangement to (2S,5R,8R,9R,10S)-10-hydroxy-8,9-isopropylidenedioxy-2-methyl-1,6-dioxaspiro[4.5]decane 3 and its (2R)-epimer 4, which closely matched the skeleton of the odour bouquet minor components of Paravespula vulgaris (L.). 相似文献
Diastereoselective alkylation of ethyl 2-methyl- and/or 2-ethylacetoacetates using the (S,S)-cyclohexane-1,2-diol as an acetal chiral auxiliary afforded enol ethers (2a-f and 5a-f) of 92->95% de in 31-70% yields. Removal of the cyclohexane-1,2-diol with BF(3)-OEt(2) afforded beta-keto esters (3 and 6) bearing a chiral quaternary carbon. The beta-keto esters could be easily converted into optically active alpha-methylated and/or alpha-ethylated alpha,alpha-disubstituted amino acids (12 and 13) in 21-99% yields using Schmidt rearrangement. 相似文献
Although the arsenic containing analogue of triptycene, 5,10--benzenoarsanthrene (E=As) was isolated some time ago [1] the related derivatives of antimony and bismuth are unknown. We now find that when 1,2-diiodotetrafluorobenzene is treated with methyllithium at -78/dg, to afford the little studied dilithiotetrafluorobenzene [2], and the appropriate metal chloride is added to the resulting solution, perfluorinated analogues of (E = As, Sb, or Bi) are obtained in good yield. These are stable volatile solids.相似文献
Specific features of melting of crystalline samples of 3-(2-R-phenoxy)propane-1,2-diols with different enantiomeric compositions
were studied by differential scanning calorimetry. The melting points and enthalpies of melting for the racemate and individual
stereoisomers were determined. Binary phase diagrams were constructed. The entropy of mixing of individual enantiomers in
the liquid phase and the free energy of formation of the racemic compound were calculated. The thermochemical data indicate
that the racemates are formed upon the crystallization of phenoxy-and 2-fluorophenoxy-containing compounds, while crystallization
of the chloro-, bromo-, and iodo-substituted analogs would form racemic conglomerates.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 225—232, February, 2006. 相似文献
A convenient and effective method for the preparation of chiral trifluoromethylated 1,2-dihydroxypropanephosphonates based on a chemoenzymatic approach was described. Ethyl trifluoromethylacetate was reacted with anion of methylphosphonate to give 2-oxo-3,3,3-trifluoropropanephosphonate and its hydrates, 2,2-dihydroxy-3,3,3-trifluoropropanephosphonates, which are reduced with sodium boronhydride affording 2-hydroxy-3,3,3-trifluoropropanephosphonates. The product thus obtained was then transferred to corresponding 1,2-vinyl-3,3,3-trifluoropropanephosphonate and followed by 1,2-dihydroxylation via potassium permanganate treatment. Enzymatic kinetic resolution of the resultant racemate by CALB or IM provided optically active 1,2-dihydroxy-3,3,3-trifluoropropanephosphonate with satisfactory chemical and enantiomeric yield. 相似文献
Asymmetric ring cleavage reaction of meso-carbobicyclic ketones by a combination of benzaldehyde, chiral cycloalkane-1,2-diol, and Lewis acid gave optically active styrenyl esters of 26-69% ee in moderate yield. The ring cleavage reaction could be applied to the construction of adjacent chiral quaternary carbons, and also to the formal synthesis of natural alkaloid (−)-alloyohimbane. 相似文献
Macroporous crosslinked poly(N-methyl-N-p-vinylbenzylacetamide) (PMVBA), poly(N-methyl-N-p-vinylbenzylurea) (PMVBU), and poly(N-methylacrylamide) (PMA) were prepared and their adsorption behaviors for tea polyphenols (TP) were investigated in aqueous solution. The results indicated that their adsorption capacities for TP followed an order as: PMVBU>PMVBA>PMA. The adsorption isotherms were fitted to Freundlich isotherm and adsorption enthalpies were calculated. It was found that Freundlich isotherm was suitable to characterize the adsorption process and their adsorption enthalpies for TP gave the same order as: PMVBU>PMVBA>PMA. Surface energy heterogeneity was analyzed by Do's model and the surface of PMVBU was shown to be the most homogeneous. Analysis of adsorption mechanism suggested that multiple hydrogen bonding, hydrophobic interaction, and pi-pi stacking were responsible for the adsorption of TP onto the adsorbents. 相似文献
Reaction of 4-[(3-carboxypropyl)amino]-6-chloro-5-nitrobenzofuroxan with 3-aminopropane-1,2-diol 1,2-dinitrate yielded 6-chloro-5-nitro-4-(2-oxopyrrolidin-1-yl)benzofuroxan instead of the expected 6-chloro-5-nitrobenzofuroxan amino derivative. 相似文献
A series of dimesitylboron (B)- or ditolylamino (N)-substituted ladder-type pentaphenylenes (PP) has been designed and synthesized. The UV-vis absorption spectra of compounds BPPN, BPPB, and NPPN reveal an identical maximum wavelength at 432 nm, which indicates that the B and N centers have very similar contributions to the extended conjugation. A rather weak solvatochromism in the UV-vis absorption spectra is observed for compound BPPN, while a remarkable solvatochromic emission is achieved even though the distance between the B and the N centers is as huge as 22 A. The photoluminescence of BPPN shows a bathochromic shift of 108 nm when the solvent polarity is increased from cyclohexane (453 nm) to acetone (561 nm). Compound BPPN acts as a colorimetric and fluorescent chemosensor with high sensitivity (10(-5) M) and selectivity for F(-) over other halogen ions. By inhibiting the charge transfer (CT) from the N center to the B center, the intense green CT emission of compound BPPN rapidly switches into the sky-blue emission of PP when F(-) is bound to the B center. Furthermore, a CT emission can be switched "on" and "off" when compound BPPB is used as F(-) sensory material. Such an intramolecular CT emission between the two B centers has so far never been reported. Corresponding studies by cyclic voltammetry and differential pulse voltammetry reveal a two-step reduction of the two bridged B centers in compound BPPB, which might suggest that the charge delocalizes through the whole molecule and that the terminal redox centers communicate through the pentaphenylene bridge. 相似文献
A chiral iminophosphite ligand based on biphenyl-2,2"-diol and its chelates with rhodium(i) and palladium(ii) were synthesized for the first time. Successful use of these compounds in asymmetric allylic substitution was demonstrated. The enantioselectivity of palladium-catalyzed alkylation of methyl pent-3-en-2-yl carbonate with dimethyl malonate reached 70%, that in the alkylation of 1,3-diphenylallyl acetate with dimethyl malonate was 88%. In the rhodium-catalyzed sulfonylation of 1,3-diphenylallyl acetate with sodium p-toluenesulfinite, the enantioselectivity was 56%. 相似文献
[reaction: see text] The Sc(OTf)3/FERRODIOL (2) complex was prepared at -78 degrees C in CH2Cl2 in the presence of 2,6-lutidine and MS 4A. The chiral scandium Lewis acid-catalyzed asymmetric Diels-Alder reaction of cyclopentadiene (3) with 3-acyloxazolidin-2-ones (4) effectively produced the adduct (5) in a high yield with good selectivity, i.e., endo/exo = 90:10 up to 91% ee (endo). 相似文献
Cyano-functionalized allylic phosphine substrates containing the ortho-metalated (R)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary were synthesized from bromoacetaldehyde dimethylacetal via a one-pot process. The diastereoselective hydrophosphination reactions of the cis- and trans-allylic phosphine substrates gave the cyano-functionalized chiral 1,2-bis(diphenylphosphino)ethane products with high yield and stereoselectivity. The subsequent organic transformation reactions of the cyano-substituted products chemoselectively afforded the formyl- and hydroxyl-functionalized chiral 1,2-diphosphine complexes with retention of stereochemistry. The coordination properties and absolute configurations of the novel 1,2-diphosphine complexes were established by single crystal X-ray crystallography. The optically pure 1,2-bis(diphenylphosphino)ethane ligands with cyano-, formyl- and hydroxyl-functionalities could be liberated in high yields from the corresponding dihalo palladium complexes by treatment with aqueous potassium cyanide. 相似文献
The adrenaline test for enzymes is a general back-titration procedure to detect 1,2-diols, 1,2-aminoalcohols and α-hydroxyketones reaction products of enzyme catalysis by colorimetry. The method was used to profile a series of esterases and lipases for their esterolytic activity on a series of carbohydrate and polyol acetates. Substrates were prepared by peracetylation and used for parallel microtiter-plate analysis of enzyme activities. This method can be used to achieve a rapid and automated characterization of a set of enzymes during HTS screening. 相似文献