Visual enantiomeric recognition of amino acid derivatives in protic solvents

Various types of chiral host molecules 2-7 based on a phenolphthalein skeleton and two crown ethers were prepared for use in visual enantiomeric recognition, and we examined their enantioselective coloration in complexation with chiral amino acid derivatives 9-22 in methanol solution. Methyl-substituted host (S,S,S,S)-3 showed particularly prominent enantiomer selectivity for the alanine amide derivatives 11 and 12. A combination of methyl-substituted host (S,S,S,S)-3 with guest (R)-11 or (R)-12 developed a purple color, whereas no color development was observed with (S)-11 or (S)-12. On the other hand, phenyl-substituted host (S,S,S,S)-6 showed deeper coloration with a wide range of (S)-beta-amino alcohols compared to that seen with host (S,S,S,S)-6 and the corresponding (R)-beta-amino alcohols at 0 degrees C. Furthermore, absorbance inversion temperatures (AIT) were observed within the range of 0-50 degrees C in many cases.     

α-萘甲醇衍生物的选择性氧化及手性联萘二酸的合成

α-萘甲醇衍生物与负载型氧化剂A(KMnO4/CuSO4.5H2O)反应,得到相应的醛(酮),产率68%~98%。光学纯的(S)-联萘二醇经A氧化制得光学纯的(S)-联萘二醛;醛经MnO2再次氧化合成了(S)-联萘二酸二甲酯;酯水解得到光学纯的(S)-联萘二酸。     

180 degree unidirectional bond rotation in a biaryl lactone artificial molecular motor prototype

A bifunctional biaryl lactone has been synthesized that should be capable of iterative unidirectional aryl-aryl bond rotation via: (1) a diastereoselective lactone ring opening, (S)-1 to (P,S)-2 or (M,S)-2; (2) a chemoselective lactonization, (P,S)-2 or (M,S)-2 to (S)-3; and (3) a chemoselective hydrolysis, (S)-3 to (S)-1. Preliminary results of a racemic sample have indicated unidirectional 180 degrees rotation with very high directional selectivity per individual artificial molecular motor molecule through the first two steps of this sequence. [reaction: see text]     

Chiral rodlike platinum complexes, double helical chains, and potential asymmetric hydrogenation ligand based on "linear" building blocks: 1,8,9,16-tetrahydroxytetraphenylene and 1,8,9,16-tetrakis(diphenylphosphino)tetraphenylene

This paper is concerned with the synthesis of 1,8,9,16-tetrahydroxytetraphenylene (3a) via copper(II)-mediated oxidative coupling, its resolution to optical antipodes, and its conversion to 1,8,9,16-tetrakis(diphenylphosphino)tetraphenylene (3b). On the basis of these chiral "linear" building blocks, three rodlike chiral complexes, triblock (R,R,R,R)-17 and (S,S,S,S)-20 and pentablock (R,R,R,R,R,R,R,R)-22, were constructed. As a hydrogen bond donor, racemic and optically active 3a was allowed to assemble with linear acceptors to afford highly ordered structures. A 1:1 adduct of 4,4'-bipyridyl and (+/-)-3a exists in a dimeric form of 3a linked by 4,4'-bipyridyl through hydrogen bonds. Pyrazine serves as a short linker between achiral parallel chains each formed by (+/-)-3a, while self-assembly of homochiral 3a into alternate parallel chains occurs in the adduct of 5,5'-dipyrimidine with (+/-)-3a. Self-assembly of (S,S)-3a or (R,R)-3a with 4,4'-dipyridyl yielded a packing of chiral double helical chains formed by chiral tetrol 3a molecules. A novel chiral ligand, (S,S)-23, derived from 3a was used in the asymmetric catalytic hydrogenation of alpha-acetamidocinnamate, yielding up to 99.0% ee and 100% conversion.     

Molecular origin for helical winding of fibrils formed by perfluorinated gelators

A chiral low-molecular weight gelator, N,N'-diperfluoroheptanoyl-1,2(R,R)- or -1,2(S,S)-diaminocyclohexane, was prepared to form a gel of acetonitrile. The conformation of the gelator in fibrils was determined by vibrational circular dichroism spectra, providing a molecular model for self-assembly in a helical fibril.     

新型手性N-烷基-3-蒎胺类化合物的合成及其抑菌活性的研究

以(1S,5S)-(－)-α-蒎烯为原料合成了系列新型(1S,2S,3S,5R)-N-烷基-3-蒎胺类化合物. (－)-α-蒎烯经硼氢化氧化、重铬酸吡啶盐(PDC)氧化得到(1S,2S,5R)-(－)-3-蒎酮; 在BF3•(C2H5)2O催化下(1S,2S,5R)-(－)-3-蒎酮与伯胺化合物反应生成Schiff碱, 再经KBH4或NaBH4还原得到(1S,2S,3S,5R)-N-烷基-3-蒎胺类化合物. 采用FT-IR, 1H NMR, 13C NMR和GC-MS等分析手段对合成所得(1S,2S,5R)-N-烷基-3-蒎烷亚胺和(1S,2S,3S,5R)-N-烷基-3-蒎胺类化合物的结构进行了表征. 考察了(1S,2S,3S,5R)-N-烷基-3-蒎胺类化合物对大肠杆菌(E. coli)、金黄色葡萄球菌(S. aureus)、枯草芽胞杆菌(B. subtilis)、荧光假单胞菌(P. fluorescens)、白色念珠菌(C. albicans)、黑曲霉(A. niger)和米根霉(R. oryzae)等细菌和真菌的抑菌和杀菌活性. 结果表明(1S,2S,3S,5R)-N-正庚基-3-蒎胺对真菌和细菌均表现出良好的杀菌和抑菌活性.     

Origin of enantioselectivity in palladium-catalyzed asymmetric allylic alkylation reactions using chiral N,N-ligands with different rigidity and flexibility

The chiral bidentate-N,N ligands, (S(a))-1, (S(a))-2, (S,S)-3 and (S,S)-4, were synthesized. They were shown to contain rigid 2-pyridinyl or 8-quinolinyl building blocks and the C(2)-symmetric chiral frameworks trans-2,5-dimethylpyrrolidinyl or (S)-(+)-2,2'-(2-azapropane-1,3-diyl)-1,1'-binaphthalene. In the (S(a))-2, and (S,S)-4 ligands pair, the 8-quinolinyl skeleton is directly bonded to the C(2)-symmetric chiral frameworks (S)-(+)-2,2'-(2-azapropane-1,3-diyl)-1,1'-binaphthalene or trans-2,5-dimethylpyrrolidinyl. This feature induces rigidity in this pair of ligands upon the N,N-framework. However, this does not occur for the (S(a))-1 and (S,S)-3 ligands, in which the presence of the -CH(2)- spacer between the frameworks bearing the nitrogen atom donors gives greater flexibility to the ligand. A further difference between the pairs of ligands is significant from the electronic properties of the chiral framework N-donor atom. The coordinating properties and the specific steric structural features of the (S(a))-1, (S(a))-2, (S,S)-3, and (S,S)-4 ligands are explained by their reactions with the [Pd(PhCN)(2)Cl(2)] and [Pd(eta(3)-PhCHCHCHPh)(mu-Cl)](2) substrates, in which the reported ligands form chelate complexes, with the exception of (S(a))-2, which failed to react with [Pd(eta(3)-PhCHCHCHPh)(mu-Cl)](2). The ligands were used in the palladium-allyl catalyzed substitution reaction of 1,3-diphenylallyl acetate with dimethylmalonate, with the best result being obtained using the (S(a))-1 ligand, giving the substitution product 2-(1,3-diphenylallyl)dimethylmalonate with an enantiomeric excess of 82% in the S form and a yield of 96%. The work demonstrates that in the presence of a steric ligand control, the electronic properties of the ligand donor atoms play a role though not significant in determining the enantioselectivity of palladium(II) catalyzed allylic substitution reactions. The results of the catalytic reaction do not provide a convincing explanation considering the coordinated chiral ligand features, as rigidity or flexibility and electronic properties of the N-donor atoms. A rationalization of the results is proposed on the basis of NMR studies and DFT calculation on the cationic complexes [Pd(eta(3)-PhCHCHCHPh)(N-N*)]CF(3)SO(3), (N-N* = (S(a))-1, 9; (S,S)-3, 10; (S,S)-4, 11).     

Molecular recognition of ketomalonates by asymmetric aldol reaction of aldehydes with secondary-amine organocatalysts

A diastereo- and enantioselective aldol reaction between aldehydes and a synthetically useful ketomalonate 1c as a hydrated form was developed, and either anti- or syn-aldol adducts having a chiral tetrasubstituted carbon center were obtained in high enantioselectivities by use of a tetrazole analogue of L-proline (S)-2 or an axially chiral amino sulfonamide (S)-3 as catalyst.     

Synthesis, characterization, and electrochemistry of cis-oxothio- and cis-bis(thio)tungsten(VI) complexes of hydrotris(3,5-dimethylpyrazol-1-yl)borate

The complexes TpWO2X react with sulfiding agents such as B2S3 or P4S10 to give the oxothio- and bis(thio)tungsten(VI) complexes TpWOSX (X = Cl(-)) and TpWS2X [X = Cl(-), S2PPh2(-); Tp = hydrotris(3,5-dimethylpyrazol-1-yl)borate]. The reaction of TpWS2Cl with (i) PPh3 in pyridine and (ii) dimethyl sulfoxide affords TpWOSCl in good overall yield. The chloro complexes undergo metathesis with alkali metal salts to yield species of the type TpWOSX and TpWS2X [X = OPh(-), SPh(-), SePh(-), (-)-mentholate]. The diamagnetic complexes exhibit NMR spectra indicative of C(1) (TpWOSX) or C(s) (TpWS2X) symmetry and IR spectra consistent with terminal oxo and thio ligation (nu(W=O), 940-925 cm(-1); nu(W=S) or nu(WS2), 495-475 cm(-1)). Crystals of (R,S)-TpWOS[(-)-mentholate] are monoclinic, space group P2(1), with a = 11.983(2) A, b = 18.100(3) A, c = 13.859(3) A, beta = 91.60(2) degrees, V = 3004.6(8) A(3), and Z = 4. Crystals of TpWS2(OPh)-CH2Cl2 are orthorhombic, space group Pbca, with a = 16.961(4) A, b = 33.098(7) A, c = 9.555(2) A, V = 5364(2) A(3), and Z = 8. The mononuclear, distorted-octahedral tungsten centers are coordinated by a tridentate Tp ligand, an alkoxy or aryloxy ligand, and two terminal chalcogenide ligands. The average W=O and W=S distances are 1.726(7) and 2.125(2) A, respectively, and the O=W=S and S=W=S angles 102.9(3) and 102.9(1) degrees, respectively. The tungsten and sulfur X-ray absorption spectra of TpWOSCl and TpWS2Cl are consistent with the presence of terminal pi-bonded thio ligands in both complexes. The thio complexes generally undergo a reversible one-electron reduction at potentials significantly more positive than their oxo analogues. The chemical, spectroscopic, and electrochemical properties of the complexes are heavily influenced by the presence of W=S pi frontier orbitals.     

Chiral trialkanolamine-based hemicryptophanes: synthesis and oxovanadium complex

[reaction: see text] A novel class of chiral hemicryptophane hosts has been synthesized in diastereoisomerically pure form, namely, M-(R,R,R)-1a/P-(S,S,S)-1a and M-(S,S,S)-1b/P-(R,R,R)-1b. The C3-symmetrical precursor 9 was prepared, using either (R)- or (S)-glycidyl nosylate, repectively, as the chiral pool reactant and subsequently cyclized (trimerized) in the presence of Sc(OTf)3. The four stereoisomers were fully characterized and displayed two pairs of mirror-image CD spectra, which were used to determine their absolute configuration. The formation of the oxovanadium(V) complex of hemicryptophane 1a is also reported.     

Hydrogenation versus transfer hydrogenation of ketones: two established ruthenium systems catalyze both

The established standard ketone hydrogenation (abbreviated HY herein) precatalyst [Ru(Cl)(2)((S)-tolbinap)[(S,S)-dpen]] ((S),(S,S)-1) has turned out also to be a precatalyst for ketone transfer hydrogenation (abbreviated TRHY herein) as tested on the substrate acetophenone (3) in iPrOH under standard conditions (45 degrees C, 45 bar H(2) or Ar at atmospheric pressure). HY works at a substrate catalyst ratio (s:c) of up to 10(6) and TRHY at s:c<10(4). Both produce (R)-1-phenylethan-1-ol ((R)-4), but the ee in HY are much higher (78-83 %) than in TRHY (4-62 %). In both modes, iPrOK is needed to generate the active catalysts, and the more there is (1-4500 equiv), the faster the catalytic reactions. The ee is about constant in HY and diminishes in TRHY as more iPrOK is added. The ketone TRHY precatalyst [Ru(Cl)(2)((S,S)-cyP(2)(NH)(2))] ((S,S)-2), established at s:c=200, has also turned out to be a ketone HY precatalyst at up to s:c=10(6), again as tested on 3 in iPrOH under standard conditions. The enantioselectivity is opposite in the two modes and only high in TRHY: with (S,S)-2, one obtains (R)-4 in up to 98 % ee in TRHY as reported and (S)-4 in 20-25 % ee in HY. iPrOK is again required to generate the active catalysts in both modes, and again, the more there is, the faster the catalytic reactions. The ee in TRHY are only high when 0.5-1 equivalents iPrOK are used and diminish when more is added, while the (low) ee is again about constant in HY as more iPrOK is added (0-4500 equiv). The new [Ru(H)(Cl)((S,S)-cyP(2)(NH)(2))] isomers (S,S)-9 A and (S,S)-9 B (mixture, exact structures unknown) are also precatalysts for the TRHY and HY of 3 under the same conditions, and (R)-4 is again produced in TRHY and (S)-4 in HY, but the lower ee shows that in TRHY (S,S)-9 A/(S,S)-9 B do not lead to the same catalysts as (S,S)-2. In contrast, the ee are in accord with (S,S)-9 A/(S,S)-9 B leading to the same catalysts as (S,S)-2 in HY. The kinetic rate law for the HY of 3 in iPrOH and in benzene using (S,S)-9 A/(S,S)-9 B/iPrOK or (S,S)-9 A/(S,S)-9 B/tBuOK is consistent with a fast, reversible addition of 3 to a five-coordinate amidohydride (S,S)-11 to give an (S,S)-11-substrate complex, in competition with the rate-determining addition of H(2) to (S,S)-11 to give a dihydride [Ru(H)(2)((S,S)-cyP(2)(NH)(2))] (S,S)-10, which in turn reacts rapidly with 3 to generate (S)-4 and (S,S)-11. The established achiral ketone TRHY precatalyst [Ru(Cl)(2)(ethP(2)(NH)(2))] (12) has turned out to be also a powerful precatalyst for the HY of 3 in iPrOH at s:c=10(6) and of some other substrates. Response to the presence of iPrOK is as before, except that 12 already functions well without it at up to s:c=10(6).     

Ruthenium complexes with chiral tetradentate imino-sulfoxide ligands

Treatment of 2-(methylsulfinyl)benzaldehyde (1) with ethylenediamine or (1R,2R)-(-)-1,2-diaminocyclohexane afforded N,N'-bis[2-(methylsulfinyl)benzylidene]ethylenediamine (L(1)) or (1R,2R)-N,N'-bis[2-(methylsulfinyl)benzylidene]-1,2-cyclohexanedia mine (L(2)), respectively. Lithiation of 2-bromobenzaldehyde diethylacetal with n-BuLi/TMEDA followed by reaction with (1R,2S,5R)-(-)-menthyl-(S)-p-toluenesulfinate afforded 2-(S)-(p-tolylsulfinyl)benzaldehyde diethyl acetal (2). Deprotection of 2 with pyridinium tosylate followed by condensation with ethylenediamine, (1R,2R)-(-)-diaminocyclohexane, or (S,S)-(+)-diaminocyclohexane afforded N,N'-bis[2-(S)-(p-tolylsulfinyl)benzylidene]ethylenediamine (L(3)), (1R,2R)-N,N'-bis[2-(S)-(p-tolylsulfinyl)benzylidene]-1,2-cyclohexanediamine ((R,R)-L(4)), or (S,S)-N,N'-bis[2-(S)-(p-tolylsulfinyl)benzylidene]-1,2-cyclohexanediamine ((S,S)-L(4)), respectively. Treatment of [Ru(PPh(3))(3)Cl(2)] with L afforded trans-[Ru(L)Cl(2)] [L = L(1) (3), L(2) (4), L(3) (5), (R,R)-L(4) ((R,R)-6), (S,S)-L(4) ((S,S)-6)]. The X-ray structures of (S(S),R(S))-4, (R,R)-6, and (S,S)-6 have been determined. The average Ru-N, Ru-S, and Ru-Cl distances in (S(S),R(S))-4 are 2.063, 2.2301, and 2.4039 A, respectively. The corresponding distances in (R,R)-6 are 2.071, 2.256, and 2.411 A, and those in (S,S)-6, 2.058, 2.2275, and 2.3831 A. Compound 3 exhibited a reversible Ru(III/II) couple at 0.56 V vs Cp(2)Fe(+/0) in CH(2)Cl(2). Treatment of 3 with AgNO(3) in water afforded the aqua compound trans-[Ru(L(1))Cl(H(2)O)][PF(6)] (7), which has been characterized by X-ray crystallography. The Ru-Cl, Ru-O, average Ru-N, and average Ru-S distances in 7 are 2.3733(6), 2.1469(16), 2.071, and 2.2442 A, respectively. Treatment of 3 with AgNO(3) followed by reaction with PPh(3) afforded [Ru(L(1))(PPh(3))(2)][PF(6)](2) (8). Treatment of [Os(PPh(3))(3)Cl(2)] with L(1) resulted in deoxygenation of one sulfoxide group of L(1) and formation of [Os(L(5))Cl(2)(PPh(3))] (9) (L(5) = N-[2-(methylsulfinyl)benzylidene]-N'-[2-(methylthio)benzylididene]ethylenediamine), which has been characterized by X-ray crystallography. The average Os-S(O), Os-N(trans to P), Os-N(trans to S), Os-P, and Os-Cl distances are 2.1931, 2.085, 2.175, 2.3641, and 2.4266 A, respectively.     

Convenient preparation and full characterization of a synthetically useful salt of the dithianitronium cation, SNSSbF6, from readily available starting materials

The synthetically useful SNSSbF6 is prepared, in good yield, from the reactions of S3N2Cl2 or S3N3Cl3 with stoichiometric amounts of AgSbF6 and S8 in liquid SO2. SNSSbF6 crystallizes monoclinic in space group C2/m (a = 9.740(2) A, b = 6.644(2) A, c = 5.334(1) A, beta = 90.58(2) degrees , Z = 2). The crystal structure was determined by standard methods and refined to R1 = 0.019 and wR2 = 0.048. The structure consists of discrete linear centrosymmetric SNS+ cations [S-N = 1.4871(10) A] and almost octahedral SbF6- anions, with weak cation-anion interactions. The lattice energy of SNSSbF6 was determined from the volume-based method as 525 +/- 32 KJ mol(-1) and the heat of formation of SNSSbF(6(s)) has been estimated as -1566 +/- 24 KJ mol(-1). The FT-IR, Raman, and (14)N NMR spectra are reported, as well as an in situ study of the reaction of S3N2Cl2 with AsF5 in SO2 solution.     

Total synthesis of (S)-(+)-curcudiol, and (S)-(+)- and (R)-(-)-curcuphenol.

A highly enantioselective synthesis of the versatile chiral synthons possessing one stereogenic center, (S)- and (R)-4-aryl-5-hydroxy-(2E)-pentenoate (3) was achieved based on the enzymatic reaction of (+/-)-3 with commercially available lipases MY-30 or OF-360 from Candida rugosa. Application of (S)-3 and (R)-3 to the total syntheses of(S)-curcuphenol (1), (S)-curcudiol (2), and (R)-curcuphenol (1), respectively, is described.     

Occupancy of the sodalite cages in the blue ultramarine pigments

A quantitative EPR study of blue ultramarine pigments has been performed in order to determine the concentration of the S(3)(-) chromophore. Copper sulfate CuSO(4) x 5H(2)O has been used as a standard, while a ruby crystal was used as an inner standard to take into account the changes of the quality factor of the cavity. These experiments show that, in the most-colored pigments, less than half of the sodalite cages are occupied by a S(3)(-) radical. In other experiments, it has been shown that the blue ultramarine pigments can be significantly modified by heating under a dynamic vacuum. The concentrations of S(3)(-) and S(2)(-), as deduced from EPR and Raman experiments, are increased after this type of treatment. These changes imply that sulfur species are transformed into S(3)(-) or S(2)(-) during this treatment. It is discussed that these sulfur species could be S(2)(-).     

The absolute configuration of the pyrrolosesquiterpenoid glaciapyrrol A

The total syntheses of the structurally unique and moderately cytotoxic pyrrolosesquiterpenoid glaciapyrrol A that has been isolated from a marine streptomycete by Macherla et al. and of seven of its stereoisomers have been performed from geraniol or nerol, respectively, using a known diastereoselective Ru-catalysed approach for the synthesis of tetrahydrofurans previously reported by Stark and co-workers. Comparison of (1)H and (13)C NMR data unambiguously clarified the relative configuration of natural glaciapyrrol A that was previously only partly solved from the available NMR data. An enantioselective synthesis was carried out resulting in the unnatural enantiomer (11S,12R,15R)-(-)-glaciapyrrol A. These data establish the absolute configuration of the natural product as (11R,12S,15S)-(+)-glaciapyrrol A.     

Preparation of (8S)-8-fluoroerythronolide A and (8S)-8-fluoroerythronolide B,potential substrates for the biological synthesis of new macrolide antibiotics

Synthetic studies are reported in the erythromycin analogue area. Reaction of trifluoromethyl hypofluorite (CF₃OF) with 8,9-anhydroerythronolide A 6,9-hemiketal (1) or 8,9-anhydroerythronolide B 6,9-hemiketal (2) afforded, as major product, (8S)-8-fluoroerythronolide A 6,9;9,ll-spiroketal (3) or (8S)-8-fluoroerythronolide B 6,9;9,ll-spiroketal (4) and, as minor product, (8S)-8-fluoroerythronolide A (5) or (8S)-8-fluoroerythronolide B (6). Hydrolysis of 3 in boiling aqueous acetic acid gave 5, 9,10-anhydro-(8S)-8-fluoroerythronolide A 6,9-hemiketal (7), (8S)-8-fluoroerythronolide A 5,9;9,12-spiroketal (9) and 5,8-epoxy-8-epi-erythronolide A (10). Analogous range of products was obtained by acid hydrolysis of 4     

Spectrofluorimetric determination of benzoimidazolic pesticides: effect of p-sulfonatocalix[6]arene and cyclodextrins

The effect of the addition of a macrocyclic host (H) such as p-sulfonatocalix[6]arene (C6S), native and modified cyclodextrins (CDs), on the fluorescence of benzoimidazolic fungicides (P), like Benomyl (BY) and Carbendazim (CZ), has been studied. The fluorescence of BY in water at pH 1.000 and 25.0 degrees C was increased in the presence of C6S, alphaCD and hydroxypropyl-beta-CD (HPCD). The association constants determined by fluorescence enhancement showed weak interactions (K(A) approximately 10(1) to 10(2) M(-1)) between the fungicide with both CDs, whereas they were stronger with C6S (K(A) approximately 10(5) M(-1)). Molecular recognition of BY for C6S was mainly attributed to electrostatic interactions, and for CDs to the hydrophobic effect and hydrogen bond formation. On the other hand, the fluorescent behaviour of CZ in the presence of C6S at pH 6.994 was interpreted as the formation of two complexes with 1:1 (P:H) and 1:2 (P:H(2)) stoichiometry, the latter being less fluorescent than the free analyte. Relative fluorescence quantum yield ratios between the complexed and free BY (phi(P:H)/phi(P)) were 2.00+/-0.05, 1.40+/-0.03 and 2.8+/-0.4 for C6S, alphaCD and HPCD, respectively. The analytical parameters improved in the presence of C6S and CDs. The best limit of detection (L(D), ng mL(-1)) was 17.4+/-0.8 with HPCD. The proposed method with C6S and HPCD was successfully applied to fortified samples of tap water and orange flesh extract with good recoveries (91-106%) and R.S.D. (< or = 2%) by triplicate analysis. The method is rapid, direct and simple and needs no previous degradation or derivatization reaction.     

Preparation and properties of cyclopentadienyl- and pentamethylcyclopentadienyl-titanium(IV) complexes with the C8H4S8 ligand, electrical conductivities of their oxidized species, and X-ray crystal structure of Ti(C5Me5)2(C8H4S8)

Ti(C5H5)2(C8H4S8) (1), Ti(C5Me5)2(C8H4S8) (2), [NMe4][Ti(C5H5)(C8H4S8)2] (3), and [NMe4][Ti(C5Me5)(C8H4S8)2] (4) [C8H4S8(2-) = 2-(4,5-ethylenedithio)-1,3-dithiole-2-ylidene)-1,3-dithiole-4,5- dithiolate(2-)] were prepared by reaction of Ti(C5H5)2Cl2, Ti(C5Me5)2Cl2, Ti(C5H5)Cl3, or Ti(C5Me5)Cl3 with Li2C8H4S8 or [NMe4]2[C8H4S8] in THF. They were oxidized by iodine, the ferrocenium cation, or TCNQ (7,7,8,8-tetracyano-p-quinodimethane) in CH2Cl2 or in acetone to afford one-electron-oxidized and over-one-electron-oxidized species, [Ti(C5H5)2(C8H4S8)].I3, [Ti(C5H5)2(C8H4S8)][PF6], [Ti(C5Me5)2(C8H4S8)].I3, [Ti(C5Me5)2(C8H4S8)][PF6], [Ti(C5H5)(C8H4S8)2].I0.9, [Ti(C5H5)(C8H4S8)2][TCNQ]0.3, [Ti(C5Me5)(C8H4S8)2].I2.4, and [Ti(C5Me5)(C8H4S8)2][TCNQ]0.3, with the C8H4S8 ligand-centered oxidation. They exhibited electrical conductivities of 1.6 x 10(-1) to 7.6 x 10(-4) S cm-1 measured for compacted pellets at room temperature. The crystal structure of 2 was clarified to consist of isolated dimerized units of the molecules through some sulfur-sulfur nonbonded contacts: monoclinic, P2(1)/c, a = 9.534(2) A, b = 18.227(2) A, c = 17.775(2) A, beta = 94.39(1) degrees, Z = 4.     

Concise syntheses of coronarin A, coronarin E, austrochaparol and pacovatinin A

Total syntheses of (+)-coronarin A (1), (+)-coronarin E (2), (+)-austrochaparol (3) and (+)-pacovatinin A (4) were achieved from the synthetic (+)-albicanyl acetate (6). Dess-Martin oxidation of (+)-albicanol (5) derived from the chemoenzymatic product (6) gave an aldehyde (7), which was subjected to Julia one-pot olefination using beta-furylmethyl-heteroaromatic sulfones (8 or 9 ) gave (+)-trans coronarin E (2) and (+)-cis coronarin E (12) with high cis-selectivity. The synthesis of (+)-coronarin A (1) from (+)-trans coronarin E (2) was achiev-ed, while (+)-cis coronarin E (12) was converted to the natural products (+)-(5S,9S,10S)-15,16-epoxy-8(17),13(16),14-labdatriene (13) and (+)-austrochaparol (3). By the asymmetric synthesis of (+)-3, the absolute structure of (+)-3 was determined to be 5S, 7R, 9R, 10S configurations. Homologation of (+)-albicanol (5) followed by allylic oxidation gave (7 alpha)-hydroxy nitrile (17), which was finally converted to the natural (+)-pacovatinin A (4) in 8 steps from (+)-albicanol (5).