Possible conformations of the seven-membered rings and relative stabilities of 1β,5α,6β,7α(H)- and 1α,5α,6β,7α(H)-guai-11(13)-en-6,12-olides

A calculation has been made by the method of molecular mechanics, using the MM2 program, of a number of stereomeres of 1,5,6,7(H)- and 1,5,6,7(H)-guai-11(13)-en-6,12-olides. The possibilities of the adoption by the seven-membered ring of particular conformations according to the type of its linkage with the 5-membered carbocycle have been considered. Questions of the influence of the orientation of the Me groups on the degree of distortion of the conformation of the seven-membered ring from the ideal and the relative stabilities of the various conformers are discussed.A. N. Nesmeyanov Institute of Organometallic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 198–203, March–April, 1991.     

A Facile Synthesis of (-)-5_αH,7β,10_α-Eudesmane-3,1 1-diene

ＡＦａｃｉｌｅＳｙｎｔｈｅｓｉｓｏｆ（－）－５_αＨ，７β，１０_α－Ｅｕｄｅｓｍａｎｅ－３，１１－ｄｉｅｎｅ￥ＮｉｎｇＺＯＵ；ＤｏｎｇＬｉａｎｇＣＨＥＮＧ；ＸｉｎＦｕＰＡＮ；ＹａｏＺｕＣＨＥＮ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，Ｌａｎｚｈｏ...     

A Convenient Synthesis of 2,4(3H,5H)-Furandione (β-Tetronic Acid)

The chemical versatility of 2,4(3H,5H)-furandione (β-tetronic acid, 1) and its synthetic applicability are of considerable current interest^1b,2a-k. The multifunctional character of this small molecule confers an intriguing synthetic potential which has prompted us to develop synthetic schemes utilizing it as a synthon for certain heterocyclic systems.     

Crystal Structure of Loliolide (5, 6,7a-Tetrahydro-6-hydroxy-4, 4, 7a-trimethyl-2 (4H)-benzofuranones)

1INTRODUCTIONThetitlecompound,C,,H,,O,(mp:146～148'C),forthefirsttime,wasiso-latedfromClinopodiumpolycephalum(Vant-)byC.Y.WuetHsuancalled"DuanXueliu"inChinesethatisusedinfolkmedicineforthetreatmentofhaemorrhagiadisease[1i.Itsstructurehasalreadybeendeterminedt2ibymeansofUV,lR,NMRandchemicalsynthesis.Sinceloliolideappearedtohaveantitumoractivity"'andim-munosuppressiveactivity'#'inrecentyears,weaffirmedthestructurebyX-raydiffractionanalysis.2EXPERIMENTALApaleyellowtransparentcry…     

5β(H)-Austricin, a New Guaianolide from Artemisia leucodes

A new sesquiterpene lactone 5(H)-austricin was isolated from white wormwood (Artemisia leucodes Schrenk.). Its structure was established by chemical and spectral methods.     

Synthesis of (+)-l-[(lα,2α,3β,4α)-2,3-Dihydroxy-4-Hydroxymethyl] -5-Methyl-2,4-(1H, 3H) Pyrimidinedione,the Carbocyclic Analogue of Ara-T

Abstract-Compound 1, the carbocyclic analogue of Ara-T, was synthesized by a four-step synthesis from (+)-(lα,2α,3β,5β)-3-amino-5-(hydroxymethyl)-l,2,-cyclopemane-diol (2), which was prepared from cyclopentadiene via a eight-step route as a potential antiviral agent.     

Synthesis of ( )-5α-Hydroxy-β-selinene and (-)-5β-Hydroxy-β-selinene

Eudesmanederivativeshavebeendrawingconsiderableattentionduetotheirwidespectrumofbiologicalproperties,particularlyantifeedant,cellgroWthinhibitoryandplantgroWthregulatingactivitiesl'2.Recently,twoepimericeudesmanederivatives( )-5a-hydroxy-6-selinene1and(-)-56-hydroxy-6-selinene2wereisolated3fromtheaerialpartsofCSubtraPicaFMell.,andtheirstructuresweredeterminedbyspectroscopicmethods.Herein,wereportafacilesynthesisofbothtwodiastereomers1and2from( )-dihydrocarvone3infivesteps,usingtheregioselect…     

SYNTHESIS OF 6,7-METHYLENEDIOXY-3-THIA-1(2H,4H)ACRIDONE AND THE RELATED THIA-ACRIDINE-PUSED HETEROCYCLIC COMPOUNDS

6,7-Methylenedioxy-3-thia-1(2H,4H)acridone and the related acridine-fused quinolines and pyridines,andalso their flavylium-perchlorates were synthesized.The structures of all these compounds prepared are characterizedby elemental analysis.IR and H-NMR spectra.     

Separation of 18α(H)-, 18β(H)-oleanane and lupane by comprehensive two-dimensional gas chromatography

18α(H)-, 18β(H)-oleanane and lupane are angiosperm-derived biomarkers that are used as age indicators for the Late Cretaceous onwards when the first proliferation of angiosperms occurred. In addition, the 18α(H)-/18β(H)-oleanane ratio is employed as a thermal maturity parameter of crude oil. However, evidence has shown that accurate quantification of these compounds has been impeded by inadequate chromatographic separation by traditional one-dimensional gas chromatography. In this study, we present the separation of 18α(H)-, 18β(H)-oleanane and lupane with comprehensive two-dimensional gas chromatography (GC×GC). Furthermore, it was observed that 18β(H)-oleanane elutes earlier than 18α(H)-oleanane in second dimension (polarity) which we attribute to steric hindrance effects. Two GC conditions have been developed in order to achieve baseline separation of the triterpenoids of interest in complex mixtures such as sediment extracts and crude oils.     

A new resolution of (1α,2β,3α,4β)-2,3-dibromocyclohex-5-en-1,4-diol by lipase from Mucor miehei

An efficient resolution of 2,3-dibromocyclohex-5-en-1,4-diol has been carried out, using Mucor miehei lipase operating in an organic solvent. The enantioforms obtained may find application in the preparation of chiral conduritols.     

Synthesis and structures of the η5-C5H5Cl(CO)2W-η1,η5-(PPh2)C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)3 and MeSi[C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)2PPh3]3 complexes

The metallation of the η⁵-C₅H₅(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ complex with BuⁿLi (THF, ?78 °C) followed by the treatment of the lithium derivative with Ph₂PCl afforded the η⁵-Ph₂PC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ complex. The reaction of the latter with η⁵-C₅H₅(CO)₃WCl in the presence of Me₃NO produced the trinuclear complex η⁵-C₅H₅Cl(CO)₂W-η¹,η⁵-(Ph₂P)C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃. The structure of the latter complex was established by IR, UV, and 1H and ³¹P NMR spectroscopy and X-ray diffraction. The reaction of MeSiCl₃ with three equivalents of LiC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₂PPh₃ gave the hexanuclear complex MeSi[C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₂PPh₃]₃.     

Synthesis of Novel 17α-Eethynyl-5-androstene-3β, 7β, 17β-triol (HE3286)Derivatives

以脱氢表雄酮为原料,经羟基乙酰化,羰基亚乙二氧基化,CrO3/3,5-二甲基吡啶氧化,硼氢化钠还原,脱17-位亚乙二氧基,脱3-位乙酰基,用叔丁基二甲基氯硅烷(TBDMSC1)保护3,7-OH,17-位环氧化,17-位开环,脱TBDMSC1保护等十步反应合成了四个新型的17α-乙炔基-5-雄甾烯-3β,7β,17β-三醇(HE3286)衍生物,其结构经1H NMR和MS表征.     

Nitroderivate vonβ,β,β-Trihalo-α,α-bis-(4-alkoxybzw. 4-oxy-phenyl)-äthanen

Zusammenfassung Auf Grund von Modellbetrachtungen wurde die Existenz der in der Literatur beschriebenenOctanitro-Derivate von ,,-Trihalo-,-bis-(4-alkoxy-phenyl)-äthanen in Zweifel gezogen. Entsprechende Untersuchungen ergaben, daß es sich bei ihnen umTetranitro-Verbindungen handelt und daß es nicht möglich ist, diese DDT-Analogen mehr als vierfach zu nitrieren. Die Konstitution der Tetranitro-Verbindungen wurde durch Abbau bewiesen: Beim ,,-Trichlor-,-bis-(3,5-dinitro-4-methoxy-phenyl)-äthan (II) durch Überführung in das entsprechende Keton (VII), beim ,,-Trichlor-,-bis-(3,5-dinitro-4-äthoxy-phenyl)-äthan (IV) durch Entalkylierung und Methylierung zu II. Der Beweis der 3,3, 5,5-Stellung der Nitrogruppen in II und IV ist auch für andere Tetranitro-Derivate von ,,-Trihalo-,-bis-(4-X-phenyl)-äthanen (X=Substituenten I. Ordnung) von Bedeutung.Mitt. II der Reihe: Stereochemische Untersuchungen in der Diphenylmethanreihe.     

Synthesis,GC-EIMS,~1H NMR,~(13)C NMR,Mechanistic and Thermal Studies of o-Xylylene-α,α'-bis (triphenylphosphinebromide)

Organophosphorous compounds containing phosphorus as an integral part have been widely used in industry, organic synthesis and optoelectronics. o-Xylylene-α,α'-bis(triphenylphosphinebromide)(OXBTPPB) is a facile reagent to convert o-quinones(e.g., 9,10-phenanthrenequinone) into polycyclic aromatic hydrocarbons(PAHs). Herein lies an improved synthetic route to OXBTPPB. The resultant was carefully characterized with GC-EIMS, 1H NMR, 13C NMR, spectroscopic techniques. The EIMS shows characteristic peaks at m/z...     

8β-hydroxyeremophil-7(11)-ene-12,8α(4β,6α)-diolide分子的晶体结构

8β-hydroxyeremophil-7(11)-ene-12,8α(4β,6α)-diolide was isolated from the Ligularia intermedia and char- acterized by MS, multi NMR and X-ray single crystal diffraction. Its crystal structure was determined as in a orthorhombic type, with space group P212121 with a=6.8519(5), b=10.7191(8), c=18.5942(14) oA, V =1365.67(18) oA3, Z=4, and the calculated density is 1.354 mg/m3. F(000)=592, μ=0.101 mm-1.     

Special Reactions of α,β-Unsaturated Ketones III [1]. Formation and Structure Elucidation of Dimers of 2-Aryl-methyleneketones: (5E)-5-Benzylidene-9β-phenyl-trans-4a-1,2,3,4,4a,5,6,7,8,9a-decahydroxanthen-4aα-ol and 3β,5β-Bis-(4-methoxyphenyl)-2α,4β,6α-trimethyl-4α-propionyl-cyclohexanone [2]

Summary.  The reaction of 2-benzylidenecyclohexanone and 1-(4-methoxyphenyl)-2-methyl-1-penten-3-one with guanidine did not yield the expected 4-phenylhexahydro-2-quinazolinamine and 4-(p-methoxyphenyl)-dihydro-2-pyrimidinamine, respectively, but nitrogen-free products which turned out as [3+3]- and [4+2]-cycloadducts of two molecules of the applied vinylogous ketone each. According to elemental analyses, mass spectra, and, in particular, NMR analyses (¹H and ¹³CNMR, HH-COSY, gs-HSQC, gs-HMBC, 1D TOCSY, NOESY, and 1D NOE difference spectra), the prepared dimers were identified as racemic (5E)-5-benzylidene-9β-phenyl-trans-4a-1,2,3,4,4a,5,6,7,8,9a-decahydroxanthen-4aα-ol and 3β,5β-bis-(4-methoxyphenyl)-2α,4β,6α-trimethyl-4α- propionylcyclohexanone, respectively. Structure and stereochemistry of the dimers are elucidated, and mechanisms for their formation are proposed. Received April 11, 2001. Accepted (revised) May 18, 2001     

1α-Acetoxy-11β(H),13-dihydrodouglanin, a New Eudesmanolide from Artemisia lehmanniana

A new sesquiterpene lactone, 1-acetoxy-11(H),13-dihydrodouglanin, was isolated fromArtemisia lehmanniana.The structure was established by spectral data and an x-ray analysis.     

6,7-二氧亚甲基-3-氮杂(硫杂)-1(2H,4H)吖啶酮及其衍生物的合成

氮杂吖啶酮;硫杂吖啶酮;杂环化合物;6;7-二氧亚甲基-3-氮杂(硫杂)-1(2H;4H)吖啶酮及其衍生物的合成     

17O, 13C, 1H NMR and IR spectroscopic investigations of (CH3)nC5H5–nRe(CO)3 analogues (n = 0–5)

¹³C, ¹H NMR investigation of the (CH_3nC₅H_5–nRe(CO)₃ Me_nCpReT) n = 0–5 analogous series showed that the signals of almost all magnetic nuclei shift upfield with increase n, which also occurs in (Me_nCp)₂M compounds (M = Fe²⁺, Co³⁺; n = 0–5). The smaller value of the C(CH₃) signal (1.5 ppm.) shifts upfield when a further methyl group is introduced into the vicinal position, this shift can be attributed to the absence of the second methyl cyclopentadienyl ring. It is noteworthy that methyl cyclopentadienyl ring coordination to the transition-metal atom results in the downfield shift of the substituted carbon atom (C_key) signal. One of the reasons for such a shift might be the reduction in screening effect of the central CpM bond π-electron current on C_key owing to nodal properties of Cp ring e-orbitals. The δ ¹³C(CO), δ ¹⁷O(CO), and v(CO) values reflect successive increases of Re → CO π-back donation with increase in n.