(S)-(-)-norlaudanosine和(S)-(-)-O,O-dimethylcoclaurine的合成

以高藜芦胺为起始原料,经N-磺酰化反应制得高藜芦磺酰胺(2);2分别与芳乙烯甲醚经对甲苯磺酸催化的Pictet-Spengler反应后用金属钠脱除Ts基团合成了(±)-norlaudanosine(5a)和(±)-O,O-dimethylcoclaurine(5b);使用半量拆分法,以N-乙酰-L-苯丙氨酸为拆分剂,制得(S)-(-)-5a和(S)-(-)-5b,其结构经1H NMR,13C NMR,IR,MS和HR-ESI-MS确证。     

微生物酶催化制备人参皂苷20(S)-Rg2,20(S)-Rh1和20(S)-PPT

摘要 人参次级皂苷具有较强的抗癌、抗癌转移等药理活性,但由于在人参中含量少或不存在,因此以人参中含量较高的主要人参皂苷制备药效更高的人参次级皂苷不仅有必要,而且很有意义．本文以微生物Microbacterium esteraromaticum GS514的培养液中分离的粗酶为催化剂水解人参皂苷Re和Rg1,并通过1H NMR和13C NMR谱进行了水解产物的结构表征．实验结果表明,反应体系中无机盐NaCl的存在与否直接影响人参皂苷Re,Rg1与粗酶液的反应结果.人参皂苷与粗酶液直接反应,人参皂苷Re不发生反应,人参皂苷Rg1通过C6所连β-D-吡喃葡萄糖的选择性水解转化成人参皂苷F1.如果该反应是在无机盐NaCl存在下进行,人参皂苷Re通过对C20 所连β-D-吡喃葡萄糖的选择性水解定向转化为20(S)-人参皂苷Rg2;人参皂苷Rg1定向转化成20(S)-人参皂苷Rh1以及20(S)-原人参三醇（PPT）.这说明NaCl的加入激活了C20β-D-吡喃葡萄糖苷酶的活性,这对定向合成不同次级人参皂苷具有重要意义.     

Overlapping resonances interference-induced transparency: The S(0) → S(2)∕S(1) photoexcitation spectrum of pyrazine

The phenomenon of "overlapping resonances interference-induced transparency" (ORIT) is introduced and studied in detail for the S(0) → S(2)∕S(1) photoexcitation of cold pyrazine (C(4)H(4)N(2)). In ORIT, a molecule becomes transparent at specific wavelengths due to interferences between envelopes of spectral lines displaying overlapping resonances. An example is the S(2)???S(1) internal conversion in pyrazine where destructive interference between overlapping resonances causes the S(0) → S(2)∕S(1) light absorption to disappear at certain wavelengths. ORIT may be of practical importance in multi-component mixtures where it would allow for the selective excitation of some molecules in preference to others. Interference-induced cross section enhancement is also shown.     

Synthesis of (S)-(−)-β-cuparenone and (S)-(−)-cuparene

A short and efficient synthesis of the title compounds is described. (S)-(−)-β-Cuparenone was prepared in 31% yield from p-tolualdehyde and mesityl oxide in eight steps. Absolute stereochemistry was established by means of a diastereoselective cyclopropanation using (R,R)-hydrobenzoin as a recoverable auxiliary.     

A Convenient Synthesis of (S)-2-Methyl and (2S)-2,3-Dimethyl Butyl Phenylsulfones from (S)-(-)-3-Methyl-γ-butyrolactone

Suitably functionalized alkylphenylsulfones have been used as building blocks for the synthesis of several modified side-chains steroids¹. We describe here the synthesis of (S)-2-methyl and (2S)-2,3-dimethyl butyl phenylsulfones (4a) and (6), which can be used for the construction of the side chain of a few marine sterols² or brassinosteroids³ as well.     

由(S)-和( R )-天冬氨酸合成( R )-和(S)-(2-苄氧乙基)环氧乙烷的改良方法

苄氧乙基环氧乙烷;不对称合成;由(S)-和( R )-天冬氨酸合成( R )-和(S)-(2-苄氧乙基)环氧乙烷的改良方法     

Facile Synthesis of (S,S)‐1,2‐Diacylamides and (S,S)‐1,2‐Diamines with C 2‐Symmetry

A series of chiral vicinal tertiary diacylamides with C ₂‐symmetry was synthesized from (S)‐α‐phenylethylamine, different aromatic aldehydes, and oxalyl chloride. The diacylamides obtained were then reduced to afford chiral vicinal diamines with C ₂‐symmetry. We propose that the diacylamides existed in four stable conformational isomers in solution because of the dihedral angle between acylamide bonds.     

用双锂引发剂制备热塑弹性体S(IB)S

苯乙烯-二烯烃热塑弹性体(SDS)是橡胶代用品和热熔压敏胶的主体材料。其粘接强度低、耐老化性差常需配以增粘剂、防老剂。苯乙烯．异戊二烯嵌段共聚物(SIS)性能比SBS和EvA优越,我国异戊二烯原料不足、价格较高。以正丁基锂为引发剂的热塑弹性体S(IA)S性能与SIS相近。本文以有机双锂为引发剂、苯乙烯、丁二烯和异戊二烯为共聚单体,采用两步加料法合成热塑弹性体S(IB)S,对其结构、性能进行了表征。     

A practical stereoselective synthesis of (S)-( - )-ofloxacin

A very efficient and practical procedure for preparation of ( S)-( - )-ofloxacin has been developed (10 steps, overall yield ≥ 45 % ) . The key step of this approach is the regioselective nucleophilic substitution of 2-position fluorine atom of 2,3,4-tirfluoronitrobenzene by (S)-glycerol acetonide.     

Photochemical reactions of [(η 5-C5H5)Mn(CO)3] with Ph2P(S)(CH2) n P(S)Ph2 [n=1, dppm(S)2; 2, dppe(S)2; 3, dppp(S)2]

Six new complexes, Mn(CO)( ⁵-C₅H₅){Ph₂P(S)(CH₂) _n P(S)Ph₂}] (1a–3a) [(1a), n=1; (2a), n=2; (3a), n=3] and [Mn₂(CO)₄( ⁵-C₅H₅)₂(cis--Ph₂P(S)(CH₂) _n P(S)Ph₂)] (1b–3b) [(1b), n=1; (2b), n=2; (3b), n=3] have been synthesized by the photochemical reaction of [( ⁵-C₅H₅)Mn(CO)₃] with Ph₂P(S)(CH₂) _n P(S)Ph₂ [n=1, dppm(S)₂; 2, dppe(S)₂; 3, dppp(S)₂]. The complexes have been characterized by elemental analysis, mass spectroscopy, f.t.-i.r. and ³¹P–[¹H]-n.m.r. spectroscopy. The spectroscopic studies reveal that coordination of the ligand iscis-chelate bidentate in [Mn(CO)( ⁵-C₅H₅){Ph₂P(S)(CH₂) _n P(S)Ph₂}] (1a–3a) and cis-bridging bidentate between two metals in [Mn₂(CO)₄( ⁵-C₅H₅)₂(cis--Ph₂P(S)(CH₂) _n P(S)Ph₂)] (1b–3b).     

(4S)-苯氧基-(S)-脯氨酸催化直接不对称羟醛缩合反应

N-乙氧羰基-(4R)-羟基-(S)-脯氨酸甲酯与苯酚的Mitsunobu反应给出N-乙氧羰基-(4S)-苯氧基-(S)-脯氨酸甲酯,后者经皂化和盐酸水解后得标题氨基酸.这一化合物(5 mol%)对映选择性催化丙酮和取代苯甲醛的羟醛缩合反应,产率67.4%～89.9%,ee最高达76.5%.     

(S)-(+)-Ipalbidine的全合成

本文报道以天然(s)-脯氨酸为原料,经过构型保持的十二步反应,合成(S)-(+)-ipalbi(dine,其氢溴酸盐呈光学活性,[a][25]D+54.1(c1,C2H5OH),在锂化性质上完全与从中国植物华佗豆(Ipomoea hardwickii Hemsl)分离出的光学活性ipalbidine(华佗豆甲碱)氢溴酸盐相同。     

(S)-异丝氨酸的合成

（S）－异丝氨酸是一种具有生物活性的β－氨基酸和重要的医药中间体。本文重点介绍了以手性化合物为原料合成（S）－异丝氨酸的路线。并对（S）－异丝氨酸的不对称合成路线进行了系统阐述。     

Synthesis of (3S,5R)-cis- and (3S,5S)-trans-3,5-Dimethylvalerolactones and Their Conversion to Biotransformation Products of (S)-5-Ethyl-5-(2′-pentyl)barbituric Acid

(R,S)-5-Ethyl-5-(2′-pentyl)barbituric acid (I)^1,2 is metabolized in vivo to give all four possible optical isomers of 5-ethyl-5-(3′-hydroxy-1′-methylbutyl)barbituric acid (II). ^3,4 From metabolism studies of pure (1′S)- I and (1′3)-I, Palmer and co-workers^4,5 were able to determine the relative amounts of each of the four isomers formed. These studies showed that (1′S)-I gave mainly one enantiomer of (1′S)-II, whereas (1′R)-I gave approximately equal amounts of both (1′R)-II enantiomers.     

(S)的(R)吉尼斯蚁警戒素合成方法研究

以樟脑衍生物(-)-莰烷磺内酰胺为原料,经N-酰基莰烷-2,10-磺内酰胺与EtMgBr进行Michael加成反应,用氢化铝锂取代磺内酰胺助剂及溴化锂取代等步骤合成了(S)和(R)吉尼斯蚁警戒素,光学纯度达98%ee。     

Short syntheses of (S)-pipecolic acid, (R)-coniine,and (S)-δ-coniceine using biocatalytically-generated chiral building blocks

The kinetic resolutions of both (±)-N-(benzyloxycarbonyl-2-(hydroxymethyl)piperidine [(±)-5] and (±)-N-(tert-butoxycarbonyl)-2-(hydroxymethyl)piperidine [(±)-6] catalyzed by the enzyme acylase I from Aspergillus species (AA-I) afforded the chiral building blocks (S)-5 and (S)-6, respectively; which were used for the syntheses of the title natural products and derivatives of (S)-pipecolic acid. The syntheses were short (2–4 steps) and proceeded with satisfactory overall yield.     

State-to-state quantum dynamics of the N(4S) + OH(X2Π) → H(2S) + NO(X 2Π) reaction

Quantum state-to-state dynamics for the N((4)S) + OH(X(?2)Π) → H((2)S) + NO(X(?2)Π) reaction is reported on an accurate ab initio potential energy surface of the lowest triplet electronic state (a(3)A(")) of HNO∕HON. It was found that the reaction is dominated by long-lived resonances supported by the HNO and HON wells. Significant non-reactive scattering was observed, indicating substantial deviations from the statistical limit. Due to the large exothermicity of the reaction, the NO product has hot internal state distributions: its rotational state distribution is inverted and peaks near the highest accessible rotational level; and its vibrational state distribution extends to υ = 10 and decays monotonically with the vibrational quantum number. In particular, the predicted product vibrational distribution is in reasonably good agreement with experiment. The calculated differential cross section is dominated by scattering in both the forward and backward directions, consistent with the formation of reaction intermediates.     

DiastereoselectiveandEnantioselectiveSynthesisof(1S,2S)-2-Ethyl-1-aminocyclopropaneCarboxylicAcid

During the last decade, 1-aminocyclopropanecarboxylic acid and its derivatives (ACCS) have attracted increasing attention of organic and bioorganic chemists due to their outstanding biological properties, ranging from antimicrobial, insecticidal, plant growth and fruit ripening controls, etc.1. Moreover, the three-membered carbocycle provides building blocks of unprecedented synthetic potential because it undergoes selective ring opening, ring enlargement or cycloaddition reactions2. The mo…     

Synthesis of betulonic acid S,S′-bis(carboxymethyl) dithioketal

Russian Chemical Bulletin - Betulonic acid S,S′-bis(carboxymethyl) dithioketal was obtained by condensation of betulonic and thioglycolic acids.     

Synthesis of (S,S)-isodityrosine by Dötz benzannulation

[reaction: see text] A synthesis of (S,S)-isodityrosine 1, a naturally occurring, key structural subunit of numerous biologically active macromolecules, is described. A formal [3 + 2 + 1] cycloaddition (D?tz benzannulation) approach was utilized to simultaneously construct an aromatic ring and the diaryl ether linkage in one step. This key step was extended to the synthesis of (S,S)-isodityrosine in two separate convergent synthetic routes. This method demonstrates a novel and mild method for the synthesis of diaryl ethers.