Chiral Resolution of β-dl-Phenylalanine Using Chiral Macrocyclic Nickel(Ⅱ) Complexes

The reactions of chiral four-coordinated nickel（Ⅱ） complex [Ni（RR-L）]（ClO4）2/[Ni（SS- L）]（ClO4）2 with β-dl-phenylalanine in acetonitrile/water gave a six-coordinated enantiomer of [Ni（RR-L）（β-d-HPhe）]（ClO4）2（1） and [Ni（SS-L）（β-l-HPhe）]（ClO4）2（2）, respectively（L = 5,5,7, 12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, HPhe = phenylalanine）. Single-crystal X-ray diffraction analyses revealed that the nickel（Ⅱ） atom displays a distorted octahedral coordination geometry by coordinating with four nitrogen atoms of L in a folded configuration, and two carboxylate oxygen atoms of β-d/l-HPhe in cis-position in both complexes. The monomers of [Ni（RR-L）（β-d-HPhe）]2＋ and [Ni（SS-L）（β-l-HPhe）]2＋ are connected through intermolecular hydrogen bonds to generate one-dimensional zigzag chains, respectively. The homochiral natures of 1 and 2 are confirmed by the results of CD spectroscopy.

Lipase immobilized on HOOC-MCF:A highly enantioselective catalyst for transesterification resolution of (R,S)-1-phenylethanol

Pseudomonas cepacia lipase （PSL） immobilized on the carboxyl-functionalized meso-cellular foams （HOOC-MCF） was used for the transesterification resolution of （R,S）-l-phenylethanol in organic solvent. The results showed that the ee value of （S）-1- phenylethanol and （R）-1-phenylethyl acetate reached 99% with 50% conversion of 1-phenylethanol using toluene as solvent. Furthermore, it was found that PSL/HOOC-MCF exhibited high enantioselectivity in organic solvent with log P ≤ 2 such as toluene and hexane.

Attempt to Resolute Chiral Clusters by Optically Active Hydrazide

A new kind of hydrazone (I) diastereoisomers was prepared with enantiomeric hydazide (II) and chiral cluster (III), which was characterized by HMBC. Unfortunately, the mixture could not be separated into pure diastereoisomer. This could be a direction to separate the racemic chiral clusters.

Chiral Recognition and Resolution Based on Helical Polymers

Helical polymers have attracted a great deal of attention and been extensively investigated due to their various applications.One of the most importa nt applicati ons of helical polymers is chiral recog nition and resolutio n ofe nan tiomersforthe reas on that a pair of e nan tiomers is comm only with differe nt physiological and toxicological behaviors in biological systems.Helical polymers usually prese nt un expected high chiral recogniti on ability to a variety of racemic compo unds.Whatzs more,the chiral recog nition and resolution abilities of the system are depe ndent on the highly ordered helical structures of the helical polymers.This mini review mainly focuses on the recent progress in chiral recognition and resolution based on helical polymers.The synthetic methodology for helical polymers is firstly discussed briefly.Then recent advances of chiral recog nition and resoluti on systems based on helical polymers,especially polyacetylenes and polyisocya nides,are described.We hope this mini review will in spire more in terest in developing helical polymers and en courage further advances in chiral-related disciplines.

Thermodynamic Resolution of Pharmaceutical Precursor Modafinil Acid on the Basis of Chiral-at-Metal Strategy

Chiral-at-metal strategy was developed to resolve the essential sulfoxide pharmaceutical intermediates R-modafinil acid and its ana-logues with high yields and ee values.The efficient resolution process was achieved based on the diastereoselective discrimination caused by hydrogen bond and intramolecular π-π interaction between chiral-at-metal center and the coordinated chiral sulfoxide ligands.Moreover,the chiral Ir(lll)receptor can be reused with complete retention of their configurations and without the loss of reaction activity and enantioselectivity.This work provides a new access to synthesize R-modafinil acid as well as its analogues and develops the application of chiral-at-metal strategy in chiral resolution.

Chiral Coordination Metallacycles/Metallacages for Enantioselec-tive Recognition and Separation

In recent years,chiral discrete supramolecular coordination complexes have attracted increasing interest as simple enzyme mimetics owing to their aesthetic architectures and potential applications in chiral science.This review summarizes the recent advances on chiral coordination metallacy-cles/metallacages with inherent cavities for enanti on selective recog nition and separation,including their design principles and synthesis,the in troduc-tion of chirality and functionality,structural adaptability,and host-guest bonding in enantioselective process.Finally,the perspectives on the remain-ing challenges and future opportunities are presented.

Extraction of Phenylalanine Phase Systems Containing Enantiomers by Aqueous Two Combinatorial Chiral Selector

In order to obtain a better enantioselectivity of phenylalanine enantiomers and establish the optimal chiral ex- traction conditions, the distribution behavior was investigated in aqueous two-phase systems which were composed of polyethylene glycol and ammonium sulfate containing combinatorial chiral selector： β-cyclodextrin and HP-β-cyclodextrin. The influence of the molar concentration ratio of combinatorial chiral selectors, the total molar concentration of combinatorial chiral selectors, pH value, buffer type and its concentration were thoroughly studied, respectively. The results show that the enantioselectivity reaches 1.53 under the optimal chiral extraction conditions This extraction is a potential economical and effective way for chiral resolution.

Aphamines A-C,dimeric acyclic diterpene enantiomers from Aphanamixis polystachya

Aphamines A-C(1-3),three pairs of acyclic diterpene dimer enantiomers with an unprecedent ploymerization pattern,were discovered from Aphanamixis polystachya by NMR-guided isolation and chiral resolution.The elucidation of their novel carbon skeletons was achieved based on spectroscopic analysis,exciton chirality,and calculated electronic circular dichroism(ECD).Plausible Claisen rearrangement,5-exo-trig cyclization,and reduction reactions may play important roles in the polymeric biosynthesis pathway.Compounds 1 and 3 showed inhibitory effects on nitric oxide(NO)production(IC_(50):6.71-15.36 μmol/L) and reduced the expression of iNOS in LPS-induced RAW 264.7 macrophages.

Applications of the crystallization process in the pharmaceutical industry

The applications of the crystallization technique in the pharmaceutical industry as a purification and separation process for the isolation and synthesis of pure active pharmaceutical ingredients(API),co-crystals,controlled release pulmonary drug delivery,and separation of chiral isomers are briefly discussed using a few case studies.The effect of process variables and solvent on the polymorphism and morphology of stavudine is discussed.The implementation of external control in the form of feedback and real-time optimal control using cooling and antisolvent crystallization of paracetamol in water-isopropyl alcohol is introduced.Two methods to prepare micronsized drug particles,namely,micro-crystallization and polymer-coated API-loaded magnetic nanoparticles for pulmonary drug delivery,are discussed.The significance of co-crystals in drug administration is highlighted using the theophylline-nicotinamide co-crystal system.Resolution of chloromandelic acid derivatives,a racemic compound,is achieved using direct crystallization and diastereomeric salts crystallization.The crystal structures of diastereomeric salts of chloromandelic acid and phenylethylamine are determined.The structure comparison between the less soluble and more soluble salts shows that weak interactions such as CH/πinteractions and van der Waals forces contribute to chiral recognition when the hydrogen bonding patterns are similar.

Sarcocinerenoids A—J,Eight Rare Capnosane-Type and Two New Cage-Type Cembranoids with Promoting Angiogenesis Activity from the South China Sea Soft Coral Sarcophyton cinereum

Backgroundand Originality Content,Cembranoids are a structurally diverse class of diterpenoids commonly occurring in marine and terrestrial organisms.(+)-Cembrene was the first reported cembranoid diterpenoid discovered in 1962,l and more than 1400 cembranoid diterpenoids have been identified in the last six decades,[2]Cembranoids are characterized by a 14-membered carbocyclic ring,an isopropyl group and three methyl groups,which form their core carbon skeleton.Enzymatic processes such as oxidation,oxidative rearrangements and transannular cyclizations occur in organisms,leading to the formation of distinctive specialized metabolites such as epoxide,lactone,ester,furan,pyrane and other ringbased cembranoids.[2-3]