Synthesis and Polymerization of Optically Active Di-L-Menthyl Itaconate

Optically active di-L-menthyl itaconate (DMI) was prepared from itaconic acid and L-menthol. DMI was polymerized in bulk at 80°C to give a chiral homopolymer having a specific rotation of -76.9°. DMI (M ₁) was copolymerized with styrene (ST, M ₂), N-cyclohexylmaleimide (CHMI, M ₂), vinyl acetate (VAc, M ₂) and methyl methacrylate (MMA, M ₂) with azobisisobutyronitrile in benzene at 50°C. The monomer reactivity ratios (r ₁, r ₂) and Alfrey-Price Q, e values were determined as r ₁ = 0.56, r ₂ = 0.55, Q ₁ = 0.76, e ₁ = 0.29 for DMI-ST; r ₁ = 0.0, r ₂ = 5.6 for DMI-MMA; r ₁ = 0.0, r ₂ = 0.25 for DMI-VAc; and r ₁ = 0.31, r ₂ = 0.56 for DMI-CHMI. The chiroptical properties of the polymers were investigated.     

手征性杂氮钛三环化合物的合成

杂氮钛三环(titatrane)(Ⅰ)是一类具有五配体特殊结构的杂环化合物,由于对其合成工作研究的不多,所以这类化合物的一些性质还鲜为人知。我们对杂氮钛三环的合成方法做了改进,将手性中心引入到这类化合物中,合成了下列结构图中(Ⅱ)所示的具有手性的杂氮钛三环。     

旋光性高分子的合成（下）

旋光性高分子的合成（下）刘引烽，华家栋（上海科技大学化学系，上海，２０１８００）４不对称聚合由外消旋手性单体制备旋光性高分子必须通过选择性聚合才能实现。选择性聚合是指外消旋的两个对映异构单体进行聚合时，由于体系中存在着某种不对称的诱导因素，其中之一比...     

Synthesis,Characterization, Polymerization of Optically Active Terminal Epoxides and Episulfides Bearing Bulky Groups

A simple and efficient protocol was developed for the syntheses of optically active epoxides(2a-2d) via the reactions of epichlorohydrin with organometallic reagents with steric hindrance at low temperature. On this basis, episulfides(3a-3d) were obtained with high e.e. values by the reaction of the corresponding epoxides with NH₄SCN. The configuration of thiiranes was opposite to that of the corresponding epoxides. Then, epoxides 2a-2d were anionically polymerized and the poly-R-2a(or poly-S-2a) was proved to keep a stable one-handed helical conformation in solution. The oligomers[degree of polymerization(DP)=2-5] were obtained when the thiiranes(3a, 3b and 3c) were used to polymerize.     

Synthesis of Conjugated Optically Active Polymetallocenes

The development of methodology for synthesizing new materials in which metal atoms are linked by hydrocarbons whose electronic conjugation is unbroken is described. The fundamental idea is to twist the hydrocarbons into helices. By attaching bulky groups to their precursors, the helices can be made to twist mainly in one direction. The molecules synthesized are helicenes capped by five-membered rings to which metals are attached. If the size of the helix is chosen appropriately, a polymeric structure forms in which hydrocarbon rings and metal atoms alternate. An oligomer with Structure 22 is the first such material prepared. It and related structures might be precursors of molecular solenoids, examples of which are not yet known.     

Synthesis of Optically Active α-Hydroxyalkylphosphonates

Russian Journal of General Chemistry -     

Synthesis of Optically Active P‐Chiral and Optically Inactive Oligophosphines

A series of optically active P‐chiral oligophosphines (S,R,R,S)‐ 2 , (S,R,S,S,R,S)‐ 3 , (S,R,S,R,R,S,R,S)‐ 4 , and (S,R,S,R,S,R,R,S,R,S,R,S)‐ 5 with four, six, eight, and 12 chiral phosphorus atoms, respectively, were successfully synthesized by a step‐by‐step oxidative‐coupling reaction from (S,S)‐ 1 . The corresponding optically inactive oligophosphines 1′ – 5′ were also prepared. Their properties were characterized by DSC, XRD, and optical‐rotation analyses. While optically active bisphosphine (S,S)‐ 1 and tetraphosphine (S,R,R,S)‐ 2 behaved as small molecules, octaphosphine (S,R,S,R,R,S,R,S)‐ 4 and dodecaphosphine (S,R,S,R,S,R,R,S,R,S,R,S)‐ 5 exhibited the features of a polymer. Furthermore, DSC and XRD analyses showed that hexaphosphine (S,R,S,S,R,S)‐ 3 is an intermediate between a small molecule and a polymer. Comparison of optically active oligophosphines 1 – 5 with the corresponding optically inactive oligophosphines 1′ – 5′ revealed that the optically active phosphines have higher crystallinity than the optically inactive counterparts. It is considered that the properties of oligophosphines depend on the enantiomeric purity as well as the oligomer chain length.     

Synthesis and Reactions of Optically Active 1,3-Diols

The ‘syn’-1,3-diols 3 , 4 and 5 with a C₇, C₆, and C₅ chain, respectively, were synthesized from methyl hydrogen 3-hydroxyglutarate ( 2 ; Schemes 1 and 2). The latter is available in (R)- and (S)-configuration. Octyl (3R)-4-chloro-3-hydroxybutanoate ( 17 ) is an alternative starting material for the preparation of 5 (Scheme 3.) The epoxide 20 , derived from 5 in a one-pot reaction, is a versatile synthon, which selectively reacts with a great number of nucleophiles (Scheme 4).     

Synthesis of Optically Active Hydroxyesters Using Biocatalysts

Optically active hydroxyesters were prepared using the fungusAspergillus nigerand the yeastSacharomyces cerevisiae.Substrate is converted highly specifically into optically active isomers with 95% purity. The R-hydroxyester was isolated by asymmetric reduction. (R,R)-Tartaric acid of 60% optical purity was used as an inductor     

Synthesis of Optically Active beta-Amino Acid N-Carboxyanhydrides

Methodology has been developed for the general synthesis of optically active beta-amino acid N-carboxyanhydrides (beta-NCAs) through cyclization of N(beta)-Boc or N(beta)-Cbz beta-amino acids using phosphorus tribromide. The formation of beta-NCAs was confirmed by spectroscopy as well as an X-ray structural determination of beta-homoalanine-N-carboxyanhydride. The beta-NCA molecules could be polymerized in good yield to give optically active poly(beta-peptides) that adopt stable chiral conformations in solution. For example, helical oligo(L-beta-homophenylalanine) was synthesized by polymerization of L-beta-homophenylalanine-N-carboxyanhydride.     

An Efficient Synthesis of Racemic and Optically Active Telluromethionine

A direct and efficient route for the construction of racemic and optically active L-telluromethionine (L-Te-Met) starting from the readily available hydrochloride salt of α-amino-γ-butyrolactone and lithium methyltellurolate is described. The reaction has been successfully scaled up to afford gram quantities of L-Te-Met in 75–80% yield.     

Chemo-Enzymatic Synthesis of Optically Active Amino Acids and Peptides

The industrial alkaline protease, alcalase, is stable and active in a high concentration of organic solvents and useful as a biocatalyst for (i) diastereoselective hydrolysis of peptide esters and preparation of racemization-free peptides; (ii) selective incorporation of esters of D-amino acid into peptides in t-butanol via a selective hydrolysis of esters of D,L-amino acid, followed by using the unhydrolyzed D-esters as a nucleophile in a kinetically controlled peptide bond formation; (iii) resolution of esters of amino acid in 95% t-butanol/5% water, followed by saponification of the unreacted esters to offer both enantiomers with high yield and optical purity; (iv) completely resolve amino-acid esters with high yield and optical purity via in situ racemization of the unreacted antipode catalyzed by pyridoxal 5-phosphate; (v) cryobioorganic synthesis of peptides with increased yields 15%–40% of peptide bond formation by reaction at 5 °C instead of 25–30 °C of a kinetically controlled enzymatic reaction in alcohols.     

旋光性物质的生理活性与不对称合成

不同构型的化合物具有不同的生理活性和不同的用途。所以,获得单一构型的化合物就成为有机化学家的一项重大研究课题。堪与酶相媲美的手性过渡金属络合物催化剂的问世把不对称合成的研究推向了一个新的境界。不对称合成作为一种新的合成方法,已不再只是一个纯粹的理论领域,它完全有可能在工业生产中获得广泛的应用。     

Optically Active Conjugated Polymer from Solvent Chirality Transfer Polymerization in Monoterpenes

Disubstituted acetylene monomers [1,2‐diphenylacetylenes (DPAs: DPA‐pC1, DPA‐mC1, DPA‐pC8); 1‐phenyl‐2‐hexylacetylene (PHA‐pC1)] are tested for asymmetric polymerization in chiral monoterpenes used as solvents and compared with the corresponding monosubstituted acetylene monomer [1‐phenylacetylene (PA‐pC1)]. DPA‐pC1 containing a trimethylsilyl group in the para‐position of the phenyl ring produces an optically active polymer with a large Cotton effect, despite the absence of a stereogenic center. The polymer sample obtained by polymerization in 87% ee (–)‐α‐pinene shows the strongest CD signal (g_CD value at 385 nm: ∼3.2 × 10⁻³). The Cotton bands of the polymers obtained in (–)‐ and (+)‐α‐pinenes show the opposite sign in the CD signals. Theoretical calculations show that only the cis‐cisoid model adopts a helical conformation. A time‐correlated single photon counting experiment shows that the emission of the chiral polymer originates from a virtually single excited species with a 98% component fraction. This polymer solution does not show any significant decrease in g_CD value over a wide temperature range of 20 to 80 °C. No noticeable decrease in the g_CD value is detected when the polymer solution is kept at relatively low temperatures for a prolonged period (35 d). In contrast, the other polymers show no CD signal.

     

光学活性双氨基酸的合成

光学活性的双氨基酸作为一类非天然的氨基酸合成子, 在医药、农药和肽类合成中有着重要的作用. 评述了近年来关于光学活性双氨基酸合成的进展.     

手性环胍衍生物的合成

以L-天冬酰胺为原料经十步反应合成了光学纯的手性双环胍, 总收率为2.2%. 这一合成方法的优点是避免使用剧毒的硫光气和气味难闻的有机硫化物     

Biotransformation In Enantioselective Synthesis of Optically Active Compounds

Transformation catalyzed by enzymes and microorganisms (biotransformation) is now well recognized as valuable tool in preparation of chiral intermediates. In this presentation the microbial reduction by G38, a fungus isolated from soil, PPL catalyzed acylation of a meso-diol and synthesis of (R)-cyanohydrins by (R)-oxynitrilase under microaqueous medium were described.     

光学活性黄烷酮类化合物的不对称合成研究进展

简要介绍了通过手性诱导、有机小分子催化和1,4-共轭加成反应合成具有光学活性的黄烷酮类化合物的研究进展,参考文献24篇。