STUDY ON THE REACTION OF N－ALKYLPHENOTHIAZINE RADICAL CATIONS WITH 2， 4－DINITROPHENYLHYDRAZINE

ＳＴＵＤＹ　ＯＮ　ＴＨＥ　ＲＥＡＣＴＩＯＮ　ＯＦ　Ｎ－ＡＬＫＹＬＰＨＥＮＯＴＨＩＡＺＩＮＥ　ＲＡＤＩＣＡＬ　ＣＡＴＩＯＮＳ　ＷＩＴＨ　２，　４－ＤＩＮＩＴＲＯＰＨＥＮＹＬＨＹＤＲＡＺＩＮＥＳＴＵＤＹＯＮＴＨＥＲＥＡＣＴＩＯＮＯＦＮ－ＡＬＫＹＬＰＨＥＮ...     

STUDY ON THE SYNTHESIS OF N~6 AROMATIC HETEROCYCLIC METHYL SUBS

ＳＴＵＤＹ　ＯＮ　ＴＨＥ　ＳＹＮＴＨＥＳＩＳ　ＯＦ　Ｎ~６　ＡＲＯＭＡＴＩＣ　ＨＥＴＥＲＯＣＹＣＬＩＣ　ＭＥＴＨＹＬ　ＳＵＢＳＴＩＴＵＴＥＤ　ＡＤＥＮＯＳＩＮＥ　ＡＮＤ　ＡＤＥＮＩＮＥＢＹ　ＤＩＭＲＯＴＨ　ＲＥＡＲＲＡＮＧＥＭＥＮＴ　ＲＥＡＣＴＩＯＮ?..     

STUDIES ON THE CONSTITUENT OF THE ACTIVE COPPER CATALYSIA IN CYCLOPROPANATION REACTIONS

ＳＴＵＤＩＥＳＯＮＴＨＥＣＯＮＳＴＩＴＵＥＮＴＯＦＴＨＥＡＣＴＩＶＥＣＯＰＰＥＲＣＡＴＡＬＹＳＩＡＩＮＣＹＣＬＯＰＲＯＰＡＮＡＴＩＯＮＲＥＡＣＴＩＯＮＳ￥ＥｒＬｅＺＡＮＧ；ＰｉｎｇＬＩ；ＢｉｎｇＦａｎｇＨＵ（ＤｅｐａｒｔｍｅｎｔｏｆＡｐｐｌｉｅｄＣｈ...     

STUDY ON THE RELATIONSHIP BETWEEN MELTING POINT AND ACID DENATURING ACIDITY OF DNA BY ULTRAVIOLET SPECTROMETER

ＳＴＵＤＹ　ＯＮ　ＴＨＥ　ＲＥＬＡＴＩＯＮＳＨＩＰ　ＢＥＴＷＥＥＮ　ＭＥＬＴＩＮＧ　ＰＯＩＮＴ　ＡＮＤ　ＡＣＩＤ　ＤＥＮＡＴＵＲＩＮＧ　ＡＣＩＤＩＴＹ　ＯＦ　ＤＮＡ　ＢＹ　ＵＬＴＲＡＶＩＯＬＥＴ　ＳＰＥＣＴＲＯＭＥＴＥＲＳＴＵＤＹＯＮＴＨＥＲＥＬＡＴ...     

STUDIES ON THE RELATIONSHIP BETWEEN THE HELICAL STRUCTURE AND OPTICAL ACTIVITIES OF SOME CHIRAL CYCLICESTERS Ⅰ

ＳＴＵＤＩＥＳＯＮＴＨＥＲＥＬＡＴＩＯＮＳＨＩＰＢＥＴＷＥＥＮＴＨＥＨＥＬＩＣＡＬＳＴＲＵＣＴＵＲＥＡＮＤＯＰＴＩＣＡＬＡＣＴＩＶＩＴＩＥＳＯＦＳＯＭＥＣＨＩＲＡＬＣＹＣＬＩＣＥＳＴＥＲＳⅠ￥ＢｉｎｇＤＥＮＧ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒ...     

SYNTHESIS AND X－RAY STRUCTURE OF A NEW PYRRYL SUBSTITUTED PHOTOCHROMIC FULGIDE

ＳＹＮＴＨＥＳＩＳＡＮＤＸ－ＲＡＹＳＴＲＵＣＴＵＲＥＯＦＡＮＥＷＰＹＲＲＹＬＳＵＢＳＴＩＴＵＴＥＤＰＨＯＴＯＣＨＲＯＭＩＣＦＵＬＧＩＤＥＳＹＮＴＨＥＳＩＳＡＮＤＸ－ＲＡＹＳＴＲＵＣＴＵＲＥＯＦＡＮＥＷＰＹＲＲＹＬＳＵＢＳＴＩＴＵＴＥＤＰＨＯＴＯＣＨＲ...     

STUDIES ON THE REACTIVITY OF CYCLOAROMATIZATION REACTION VIA a－OXO KETENE DITHIOACETALS

ＳＴＵＤＩＥＳＯＮＴＨＥＲＥＡＣＴＩＶＩＴＹＯＦＣＹＣＬＯＡＲＯＭＡＴＩＺＡＴＩＯＮＲＥＡＣＴＩＯＮＶＩＡａ－ＯＸＯＫＥＴＥＮＥＤＩＴＨＩＯＡＣＥＴＡＬＳ￥ＱｕｎＬＩＵ；ＺｈｉＬｉｎｇＷＡＮＧ；ＳｈｕＪｉａＺＨＡＮＧ；ＺｈｉＹｕｎＹＡＮＧ（Ｄｅｐａｒ...     

MOLECULAR MECHANICAL AND QUANTUM CHEMICAL CALCULATION ON ACYLATION REACTIVITY FOR 1－（NITRO SUBSTITUTED ANILINO）－4－SUBSTITUTED－2，6－PIPERAZINEDIONES

ＭＯＬＥＣＵＬＡＲＭＥＣＨＡＮＩＣＡＬＡＮＤＱＵＡＮＴＵＭＣＨＥＭＩＣＡＬＣＡＬＣＵＬＡＴＩＯＮＯＮＡＣＹＬＡＴＩＯＮＲＥＡＣＴＩＶＩＴＹＦＯＲ１－（ＮＩＴＲＯＳＵＢＳＴＩＴＵＴＥＤＡＮＩＬＩＮＯ）－４－ＳＵＢＳＴＩＴＵＴＥＤ－２，６－ＰＩＰＥＲＡＺ...     

AB INITIO CONFIGURATION INTERACTION STUDY OF THE ELECTRONIC AND GEOMETRIC STRUCTURE OF MIXED NEUTRAL AND CATIONIC BLi_k（k＝1~7）CLUSTERS

ＡＢＩＮＩＴＩＯＣＯＮＦＩＧＵＲＡＴＩＯＮＩＮＴＥＲＡＣＴＩＯＮＳＴＵＤＹＯＦＴＨＥＥＬＥＣＴＲＯＮＩＣＡＮＤＧＥＯＭＥＴＲＩＣＳＴＲＵＣＴＵＲＥＯＦＭＩＸＥＤＮＥＵＴＲＡＬＡＮＤＣＡＴＩＯＮＩＣＢＬｉ_ｋ（ｋ＝１~７）ＣＬＵＳＴＥＲＳＨｕａＢｅｉＺＨ...     

STUDIES ON THE NON－ISOTHERMAL KINETICS OF THERMAL DECOMPOSITIONS OF THE COMPLEXES OF Cd（II）WITH O－VANILLIN THIOSEMICARBAZONE AND IRON（III）WITH 2－［（O－HYDROXYBENZYLIDENE）AMINO］PHENOL AND PYRIDINE

ＳＴＵＤＩＥＳＯＮＴＨＥＮＯＮ－ＩＳＯＴＨＥＲＭＡＬＫＩＮＥＴＩＣＳＯＦＴＨＥＲＭＡＬＤＥＣＯＭＰＯＳＩＴＩＯＮＳＯＦＴＨＥＣＯＭＰＬＥＸＥＳＯＦＣｄ（ＩＩ）ＷＩＴＨＯ－ＶＡＮＩＬＬＩＮＴＨＩＯＳＥＭＩＣＡＲＢＡＺＯＮＥＡＮＤＩＲＯＮ（ＩＩＩ）ＷＩＴ...     

Origin of the relative stereoselectivity of the beta-lactam formation in the Staudinger reaction

The relative (cis, trans) stereoselectivity of the beta-lactam formation is one of the critical issues in the Staudinger reaction. Although many attempts have been made to explain and to predict the stereochemical outcomes, the origin of the stereoselectivity remains obscure. We are proposing a model that explains the relative stereoselectivity based on a kinetic analysis of the cis/trans ratios of reaction products. The results were derived from detailed Hammett analyses. Cyclic imines were employed to investigate the electronic effect of the ketene substituents, and it was found that the stereoselectivity could not be simply attributed to the torquoelectronic model. Based on our results, the origin of the relative stereoselectivity can be described as follows: (1) the stereoselectivity is generated as a result of the competition between the direct ring closure and the isomerization of the imine moiety in the zwitterionic intermediate; (2) the ring closure step is most likely an intramolecular nucleophilic addition of the enolate to the imine moiety, which is obviously affected by the electronic effect of the ketene and imine substituents; (3) electron-donating ketene substituents and electron-withdrawing imine substituents accelerate the direct ring closure, leading to a preference for cis-beta-lactam formation, while electron-withdrawing ketene substituents and electron-donating imine substituents slow the direct ring closure, leading to a preference for trans-beta-lactam formation; and (4) the electronic effect of the substituents on the isomerization is a minor factor in influencing the stereoselectivity.     

Concise synthesis of the cell cycle inhibitor demethoxyfumitremorgin C

Reaction of the imine derived from L-tryptophan methyl ester and senecialdehyde with Fmoc-L-Pro-Cl induces an acyliminium Pictet-Spengler condensation, yielding a mixture of cis and trans tetrahydro-β-carbolines. Deprotection of the cis product with concomitant diketopiperazine formation afforded the natural product in 20 % overall yield.     

Total synthesis of amiclenomycin, an inhibitor of biotin biosynthesis

We describe the first synthesis of amiclenomycin, a natural product that has been found to inhibit biotin biosynthesis and, as a consequence, to exhibit antibiotic properties. Structure 1, with a trans relationship between the ring substituents. had previously been proposed for amiclenomycin on the basis of its 1H NMR spectrum. We have prepared the trans and cis isomers 1 and 2 by unequivocal routes and we conclude that the natural product is in fact the cis isomer 2. The properly substituted cyclohexadienyl rings were constructed first. A cycloaddition reaction between 1,2-di(phenylsulfonyl)ethylene and the N-allyloxycarbonyl diene 13, followed by reductive elimination of the phenylsulfinyl groups, gave the cis isomer 15. To obtain the trans isomer, the O-trimethylsilyl diene was used to give the cis hydroxylated Diels-Alder adduct 33, which was transformed into the corresponding trans amino derivative by means of a Mitsunobu reaction. The L-alpha-amino acid functionality was introduced by means of a Strecker reaction on the aldehydes 16 and 42, followed by enzymatic hydrolysis with immobilised pronase.     

Highly stereoselective radical carbonylations of gem-dihalocyclopropane derivatives with CO

A couple of radical carbonylations of gem-dihalocyclopropanes 1 using CO and Bu3SnH (formylation) or Bu3Sn(CH2CH=CH2) (allylacylation) successfully proceeded to give trans and cis adducts (2 and 3) with good to excellent stereoselectivity (trans/cis = >99/1-75/25 or 17/83-1/99). The formylation of 2,3-cis-disubstituted 1,1-dihalocyclopropanes enhanced trans selectivity (trans/cis = >99/1-95/5), whereas both 2,3-cis-disubstituted and 2-monosubstituted 1,1-dihalocyclopropanes underwent allylacylation with nearly complete trans selectivity (trans/cis = >99/1). Inherently less reactive gem-dichloro- and bromochlorocyclopropanes than gem-dibromocyclopropanes served as favorable substrates. [reaction: see text].     

2-氯-2-氧代(硫代)-1, 3, 2-二氧磷杂环己烷的甲醇解及其开环 异构化反应

报道了trans-2-氧代-2-氯-4-苯基-5,5-二甲基-1,3,2-二氧磷杂环己烷以及cis-2-硫代-2-氯-4-苯基-5,5-二甲基-1,3,2-二氧磷杂环己烷甲醇解反应的立体化学。结果表明,反应体系的酸碱性对前者甲醇解反应的立体化学有着重要影响。而硫代环磷酰氯在碱性条件下的甲醇解反应存在一个开环异构化过程。     

Aminals as substrates for sulfur ylides: a synthesis of functionalized aziridines and N-heterocycles

Sulfur ylides stabilized by Ar, vinyl, or amide groups react with five-membered-ring tert-butylsulfinyl aminals to give functionalized chiral, nonracemic aziridines in high yield and with good selectivities (up to 15:1 trans:cis, up to >95:5 trans dr, always >95:5 cis dr). The intermediate aziridines can be converted into pyrrolidines or piperidines depending on the reaction conditions.     

BiBr3-initiated tandem addition/silyl-Prins reactions to 2,6-disubstituted dihydropyrans

A tandem addition/silyl-Prins reaction efficiently affords cis-2,6-disubstituted dihydropyrans (DHPs) using 5 mol % of BiBr3 in CH2Cl2. The reaction occurs between delta-triethylsilyloxyvinyltrimethylsilanes and a variety of aldehydes to give good to excellent isolated yields of DHPs. The diastereoselectivities in the crude products are significantly affected by aldehyde substitution with electron-rich aldehydes, providing 2-3:1 (cis:trans) and neutral (or electron-poor) aldehydes affording dr > or = 19:1 (cis:trans).     

Novel stereoselective control over cis vs trans opening of benzo[c]phenanthrene 3,4-diol 1,2-epoxides by the exocyclic N(2)-amino group of deoxyguanosine in the presence of hexafluoropropan-2-ol

We describe a novel and efficient synthesis (62-84% yields) of the eight possible, diastereomerically pure, cis and trans, R and S O(6)-allyl-protected N(2)-dGuo phosphoramidite building blocks derived through cis and trans opening of (+/-)-3alpha,4beta-dihydroxy-1beta,2beta-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene [BcPh DE-1 (1)] and (+/-)-3alpha,4beta-dihydroxy-1alpha,2alpha-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene [BcPh DE-2 (2)] by hexafluoropropan-2-ol (HFP)-mediated addition of O(6)-allyl-3',5'-di-O-(tert-butyldimethylsilyl)-2'-deoxyguanosine (3) at C-1 of the epoxides. Simply changing the relative amount of HFP used in the reaction mixture can achieve a wide ratio of cis/trans addition products. Thus, the observed cis/trans adduct ratio for the reaction of DE-1 (1) in the presence of 5 equiv of 3 varied from 17/83 to 91/9 over the range of 5-532 equiv of HFP. The corresponding ratios for DE-2 (2) varied from 2/98 to 61/39 under the same set of conditions. When 1 or 2 was fused with a 20-fold excess of 3 at 140 degrees C in the absence of solvent HFP, almost exclusive trans addition (>95%) was observed for the both DEs. Through the use of varying amounts of HFP in the reaction mixture as described above, each of the eight possible phosphoramidite oligonucleotide building blocks (DE-1/DE-2, cis/trans, R/S) of the BcPh DE N(2)-dGuo adducts can be prepared in an efficient fashion. To rationalize the varying cis-to-trans ratio, we propose that the addition of 3 to 1 or 2 in the absence of solvent or in the presence of small amounts of HFP proceeds primarily via an S(N)2 mechanism to produce mainly trans-opened adducts. In contrast, increasing amounts of HFP promote increased participation of an S(N)1 mechanism involving a relatively stable carbocation with two possible conformations. One of these conformations reacts with 3 to give mostly trans adduct, while the other conformation reacts with 3 to give mostly cis adduct.     

Light-driven molecular hinge: a new molecular machine showing a light-intensity-dependent photoresponse that utilizes the trans-cis isomerization of azobenzene

[reaction: see text] A new class of molecular machine exhibits a hingelike motion upon photoirradiation. The motion (close and open) can be operated by alternate irradiation with UV and visible light. The trans/trans and cis/cis isomers are thermally stable at 40 degrees C, and the photochemical closure reaction (from trans/trans to cis/cis isomer) is dependent on the intensity of the light used because of the short-lived intermediate (trans/cis isomer).     

新的钌环丙烷化催化体系的探索(Ⅱ) 氮膦配体立体化学结构控制顺反比选择性的初步研究

本文研究了一个新的钌催化的苯乙烯环丙烷化反应催化体系。当该催化体系用三氟甲磺酸银预处理后其催化的环丙烷化反应产物的顺反比接近1：1,且顺式产物略微占优。这在环丙烷化反应中是不多见的。我们用分子力学／动力学对该催化体系进行了模拟。结果表明键能并非是决定产物顺反比的主要因素,但是对于非键能来说,由于中间体M1与苯乙烯作用生成顺式产物时的范德华作用非常强,它弥补了由静电能所引起的能量上的不利因素。所以总能量对生成顺式产物较为有利。但是由于生成顺式产物与反式产物的总能量差别不大（2．5kcal.mol^-1),所以环丙烷化产物的顺反比接近1：1。这是氮膦配体立体化学结构控制产物选择性的结果。