可回收手性配体[QN（OH）2]2PHAL催化合成紫杉醇13-C侧链

在可回收手性配体[QN(OH)2]2PHAL的催化下,通过不对称氨羟化或双羟化反应合成紫杉醇13-C侧链,两种方法的产率分别为39%,97%ee和52%,99%ee,其结构经1H NMR,IR和元素分析确证。     

Highly Enantioselective Organocatalytic Addition of Aldehydes to N‐(Phenylmethylene)benzamides: Asymmetric Synthesis of the Paclitaxel Side Chain and Its Analogues

Easily side‐tracked : A simple route to the paclitaxel side chain and its analogues is based on the (R)‐proline‐catalyzed addition of aldehydes to N‐(phenylmethylene)benzamides, followed by oxidation of the resulting protected α‐hydroxy‐β‐benzoylaminoaldehydes (92–99 % ee). Esterification of the subsequent phenylisoserine derivatives with baccatin III gives paclitaxel analogues (see scheme).

     

Highly diastereoselective and enantioselective preparation of homoallylic amines: application for the synthesis of beta-amino acids and gamma-lactams

Reactions of N-silyl- and N-aluminoimines with B-allyldiisopinocampheylborane in the presence of methanol, followed by oxidative workup furnished homoallylic amines in good yields and high ee. A 11B NMR spectroscopy study revealed that the reactions do not proceed, even at room temperature, unless a molar equivalent of water or methanol is added. The first reagent-controlled asymmetric crotylboration and alkoxyallylboration of aldimines furnishing beta-methyl or beta-alkoxy homoallylic amines in very high diastereoselectivity and enantioselectivity are reported herein. Crotylboration and alkoxyallylboration of imines proceed only with the "allyl"-boron "ate" complexes, instead of the "allyl"-dialkylboron reagents used with aldehydes. The addition of methanol is necessary for these reactions as well. Application of this methodology for the conversion of representative nitriles to beta-amino acids in two steps has been described. Additionally, a procedure for the preparation of chiral delta-amino alcohols and gamma-lactams from nitriles is also reported.     

Multistep Synthesis Using Modular Flow Reactors: Bestmann–Ohira Reagent for the Formation of Alkynes and Triazoles

Multistep in flow: The Seyferth–Gilbert reagent 1 has been applied in a flow system to rapidly synthesize terminal alkynes. The system has been further applied to synthesize triazole 3 from alcohol 2 in a three‐step oxidation/homologation/copper(I)‐catalyzed azide–alkyne cycloaddition sequence without isolation of intermediates (see scheme).

     

A Highly Stereoselective Synthesis of Glycidic Amides Based on a New Class of Chiral Sulfonium Salts: Applications in Asymmetric Synthesis

A new type of chiral sulfonium salts that are characterized by a bicyclic system has been designed and synthesized from α‐amino acids. Their corresponding ylides, which were prepared by basic treatment of the sulfonium salts, reacted smoothly with a broad array of simple and chiral aldehydes to provide trans‐epoxy amides in reasonable to very good yields and excellent stereoselectivities (>98 %). The obtained epoxy amides were found to be useful as synthetic building blocks. Thus, they were reduced into their corresponding epoxy alcohols and subjected to oxirane‐ring‐opening reactions with different types of nucleophiles.     

A Highly Stereoselective and Flexible Strategy for the Convergent Synthesis of Long‐Chain Polydeoxypropionates: Application towards the Synthesis of the Glycolipid Membrane Components Hydroxyphthioceranic and Phthioceranic Acid

A highly stereocontrolled and flexible access to biologically relevant polydeoxypropionates in optically pure form has been developed. Taking advantage of our previously established strategy for the asymmetric and stereodivergent synthesis of trideoxypropionate building blocks, we have now been able to assemble large polydeoxypropionate chains with defined configuration in a highly convergent manner. Central steps of this approach include two Suzuki–Miyaura cross‐coupling reactions with subsequent highly diastereoselective hydrogenations to join three advanced synthetic intermediates in excellent yield and with full stereochemical control. We have applied this strategy successfully towards the asymmetric synthesis of glycolipid membrane components phthioceranic acid and hydroxyphthioceranic acid, the latter of which was synthesized on a half‐gram scale.     

A New Convenient Method for the Synthesis of Formyl Ferrocene with Triethyl Orthoformate and A1C13

Formyl ferrocene was synthesized by a new convenient method with CH(EtO)₃/AlCl₃.     

A New Variant of the Claisen Rearrangement from Malonate-Derived Allylic Trimethylsilyl Ketene Acetals: Efficient, Highly Enantio- and Diastereoselective Syntheses of (+)-Methyl Dihydroepijasmonate and (+)-Methyl Epijasmonate

Complete chirality transfer occurs in the smooth Claisen rearrangement of the trimethylsilyl (TMS) ketene acetals, which were prepared from allylic malonates (R)-1 (R=pentyl, 2-(Z)-pentenyl). These are in turn accessible by enantioselective reduction/esterification or by enzymatic kinetic resolution. The cis configuration in (+)-3 was achieved by highly syn-selective epoxidation of (+)-2, followed by suprafacial 1,2-H migration.     

Asymmetric Total Synthesis of Cytotrienin A: Late-Stage Installation of C11 Side Chain onto the Macrolactam Scaffold

Cytotrienin A, an ansamycin-class antibiotic, exhibits potent apoptosis-inducing activity and has attracted much attention as a lead compound for anticancer drugs. Herein, we report a new asymmetric synthetic route to cytotrienin A, employing an unexplored approach involving the late-stage installation of a C11 side chain onto the macrolactam core. In this strategy, we utilized the redox properties of hydroquinone and installed a side chain on the sterically hindered C11 hydroxy group by the traceless Staudinger reaction. This study also demonstrated that the boron-Wittig/iterative Suzuki–Miyaura cross-coupling sequence was effective for the concise and selective construction of the (E,E,E)-conjugated triene moiety. The developed route opens new opportunities for the structure–activity relationship studies of the side chains of these ansamycin antibiotics and the preparation of other synthetic analogs and chemical probes for further biological studies.     

新方法合成LiFePO4/C

以Fe(NO3)3·9H2O、LiNO3、NH4H2PO4和蔗糖为原料,在超临界CO2流体中反应合成,进而经二次焙烧制得LiFePO4/C。 结果表明,在超临界CO2流体中经50 ℃反应24 h,在350和600 ℃焙烧后制得粒径分布在0.5~1.0 μm的纯LiFePO4/C,该材料作为锂离子电池正极的放电比容量达156.6 mA·h/g,经50次循环后容量几乎没有衰减。     

Synthesis and Photophysical Properties of Polyfluorene With Dipicolylamine Groups on the Side Chain: Highly Selective and Sensitive Detection of Histidine

Two new polyfluorenes with dipicolylamine (DPA) pendant, PF‐TDPA and PF‐HDPA, are designed and synthesized by pre‐ and post‐functionalization, respectively. PF‐TDPA with a rigid side chain shows a selective fluorescence quenching upon the addition of Cu²⁺ in a mixture solution of tetrahydrofuran and 4‐(2‐hydroxyethyl)‐1‐piperazineethanesulfonic acid (HEPES) buffer. What is more, the PF‐TDPA/Cu²⁺ complex can selectively detect histidine over other amino acids with a fluorescence recovery. In contrast, PF‐HDPA with a flexible spacer exhibits a fluorescence quenching to Cu²⁺ but slightly fluorescence recovery after the addition of histidine. This indicates that the proper distance between the two DPA groups play an important role in the detection of histidine.