Cyclization and rearrangement of diterpenoids. VI. Products of dehydration of (1R,2S,7S,10S,12S,13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.01,10.02,7]pentadecan-13-ol by phosphorus oxychloride

It has been established that on the dehydration of (1R,2S,7S,10S,12S,13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadecan-13-ol with phosphorus oxychloride in pyridine a mixture of six substances is formed, from which three previously undescribed hydrocarbons have been isolated and identified: (1R,2S,7S,10S,11R,12S,13S)-2,6,6,10,12-pentamethylpentacyclo[10.2.1.0^1,10.0^2,7.-0^11,13]pentadecane, (1R,2S,7S,10S,12R)-2,6,6,10,13-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadec-13(14)-ene, and (1R,2S,7S,10S,12R)-2,6,6,10-tetramethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadec-13(16)-ene, these being based on two new carbon skeletons.Institute of Chemistry, Institute of Applied Physics, MSSR Academy of Sciences, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 203–211, March–April, 1988.     

S2 fluorescence and ultrafast relaxation dynamics of the S2 and S1 states of a ketocyanine dye

Dynamics of the excited singlet (both the S2 and S1) states of a ketocyanine dye, namely, 2,5-bis[(2,3-dihydroindolyl)-propylene]-cyclopentanone (KCD), have been investigated in different kinds of media using steady-state absorption and emission as well as femtosecond transient absorption spectroscopic techniques. Steady-state fluorescence measurements, following photoexcitation of KCD to its second excited singlet state, reveal dual fluorescence (emission from both the S2 and S1 states) behavior. Although the intensity of the S2 --> S0 fluorescence is weaker than that of the S1 --> S0 fluorescence in solutions at room temperature (298 K), the former becomes as much as or more intense than the latter in rigid matrixes at 77 K. The lifetime of the S2 state is short and varies between 0.2 and 0.6 ps in different solvents. After its creation, the S2 state undergoes two simultaneous processes, namely, S2 --> S0 fluorescence and S2 --> S1 internal conversion. Time-resolved measurements reveal the presence of an ultrafast component in the decay dynamics of the S1 state. A good correlation between the lifetime of this component and the longitudinal relaxation times (tauL) of the solvents suggests that this component arises due to solvation in polar solvents. More significant evolution of the spectroscopic properties of the S1 state in alcoholic solvents in the ultrafast time domain has been explained by the occurrence of the repositioning of the hydrogen bonds around the carbonyl group in the excited state of KCD. In 2,2,2-trifluoroethanol, a strongly hydrogen bond donating solvent, it has even been possible to establish the existence of two distinct forms of the S1 state, namely, the non-hydrogen-bonded (or free) molecule and the hydrogen-bonded complex.     

Rotational spectroscopy and equilibrium structures of S3 and S4

The sulfur molecules thiozone S3 and tetrasulfur S4 have been observed in a supersonic molecular beam in the centimeter-wave band by Fourier transform microwave spectroscopy, and in the millimeter- and submillimeter-wave bands in a low-pressure glow discharge. For S3 over 150 rotational transitions between 10 and 458 GHz were measured, and for S4 a comparable number between 6 and 271 GHz. The spectrum of S3 is reproduced to within the measurement uncertainties by an asymmetric top Hamiltonian with three rotational and 12 centrifugal distortion constants; ten distortion constants, but an additional term to account for very small level shifts caused by interchange tunneling, are required to reproduce to comparable accuracy the spectrum of S4. Empirical equilibrium (r(e)(emp)) structures of S3 and S4 were derived from experimental rotational constants of the normal and sulfur-34 species and vibrational corrections from coupled-cluster theory calculations. Quantum chemical calculations show that interchange tunneling occurs because S4 automerizes through a transition state with D2h symmetry which lies about 500 cm(-1) above the two equivalent C2upsilon minima on the potential energy surface.     

The 11S proteasome activator: Isolation from mouse brain and the influence on peptide substrate hydrolysis of the 20S and 26S proteasomes

Purification of the 11S proteasome regulator from mouse brain was optimized; the subunit composition of the isolated protein was determined by Western blot. The dependency of 20S proteasome peptidase activity on the molar concentration of the 11S regulator was examined. The Michaelis constants of hydrolysis of the specific fluorescent substrates Suc–Leu–Leu–Val–Tyr–AMC, Ac–Arg–Leu–Arg–AMC, and Z–Leu–Leu–Glu–AMC by the 20S proteasome from BALB/c mouse brain and the 20S–11S complex were determined. It was shown that the 11S particle has almost no influence on binding of specific fluorescent substrates to the 20S proteasome, but strongly accelerates hydrolysis of all three substrates, while not affecting the rate of peptide substrate hydrolysis by the 26S proteasome.     

Cyclization and rearrangements of diterpenoids. VIII. Products of dehydration of (1S,2S,7S,10R,11S,12S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.01,10.02,7]-pentadecan-11-ol by phosphorus oxychloride

On the dehydration of (1S, 2S, 7S, 10R, 11S, 12S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadecan-11-ol by phosphorus oxychloride in pyridine a mixture of three hydrocarbons is formed: the known (1R, 2S, 7S, 10S, 11R, 12S, 13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7.0^11,13]pentadecane and the previously undescribed (1R, 2S, 7S, 10S, 11S)-2,6,6,10,12-pentamethyltetra-cyclo[9.2.2.0^1,10.0^2,7]pentadeca-12-ene and (1R, 2S, 7S, 10S, 11S)-2,6,6,10-tetramethyl-12-methylenetetracyclo[9.2.2.0^1,10.0^2,7]pentadecane, based on a new carbon skeleton.Institute of Chemistry, Moldavian SSR Academy of Sciences, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 489–497, July–August, 1989.     

Sequential oxidation of the cubane [4Fe--4S] cluster from [4Fe--4S](-) to [4Fe--4S](3+) in Fe(4)S(4)L(n)(-) complexes

Gaseous Fe(4)S(n)(-) (n = 4-6) clusters and synthetic analogue complexes, Fe(4)S(4)L(n)(-) (L = Cl, Br, I; n = 1-4), were produced by laser vaporization of a solid Fe/S target and electrospray from solution samples, respectively, and their electronic structures were probed by photoelectron spectroscopy. Low binding energy features derived from minority-spin Fe 3d electrons were clearly distinguished from S-derived bands. We showed that the electronic structure of the simplest Fe(4)S(4)(-) cubane cluster can be described by the two-layer spin-coupling model previously developed for the [4Fe] cubane analogues. The photoelectron data revealed that each extra S atom in Fe(4)S(5)(-) and Fe(4)S(6)(-) removes two minority-spin Fe 3d electrons from the [4Fe--4S] cubane core and each halogen ligand removes one Fe 3d electron from the cubane core in the Fe(4)S(4)L(n)(-) complexes, clearly revealing a behavior of sequential oxidation of the cubane over five formal oxidation states: [4Fe--4S](-) --> [4Fe--4S](0) --> [4Fe--4S](+) --> [4Fe-4S](2+) --> [4Fe-4S](3+). The current work shows the electron-storage capability of the [4Fe--4S] cubane, contributes to the understanding of its electronic structure, and further demonstrates the robustness of the cubane as a structural unit and electron-transfer center.     

Physicochemical and Functional Properties of 2S, 7S,and 11S Enriched Hemp Seed Protein Fractions

The hemp seed contains protein fractions that could serve as useful ingredients for food product development. However, utilization of hemp seed protein fractions in the food industry can only be successful if there is sufficient information on their levels and functional properties. Therefore, this work provides a comparative evaluation of the structural and functional properties of hemp seed protein isolate (HPI) and fractions that contain 2S, 7S, or 11S proteins. HPI and protein fractions were isolated at pH values of least solubility. Results showed that the dominant protein was 11S, with a yield of 72.70 ± 2.30%, while 7S and 2S had values of 1.29 ± 0.11% and 3.92 ± 0.15%, respectively. The 2S contained significantly (p < 0.05) higher contents of sulfhydryl groups at 3.69 µmol/g when compared to 7S (1.51 µmol/g), 11S (1.55 µmol/g), and HPI (1.97 µmol/g). The in vitro protein digestibility of the 2S (72.54 ± 0.52%) was significantly (p < 0.05) lower than those of the other isolated proteins. The intrinsic fluorescence showed that the 11S had a more rigid structure at pH 3.0, which was lost at higher pH values. We conclude that the 2S fraction has superior solubility, foaming capacity, and emulsifying activity when compared to the 7S, 11S, and HPI.     

Cyclization and rearrangements of diterpenoids. VIII. Products of dehydration of (1S,2S,7S,10R,11S,12S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.01,10.02,7]-pentadecan-11-ol by phosphorus oxychloride

On the dehydration of (1S, 2S, 7S, 10R, 11S, 12S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadecan-11-ol by phosphorus oxychloride in pyridine a mixture of three hydrocarbons is formed: the known (1R, 2S, 7S, 10S, 11R, 12S, 13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7.0^11,13]pentadecane and the previously undescribed (1R, 2S, 7S, 10S, 11S)-2,6,6,10,12-pentamethyltetra-cyclo[9.2.2.0^1,10.0^2,7]pentadeca-12-ene and (1R, 2S, 7S, 10S, 11S)-2,6,6,10-tetramethyl-12-methylenetetracyclo[9.2.2.0^1,10.0^2,7]pentadecane, based on a new carbon skeleton.     

Cyclization and rearrangements of diterpenoids. IX. Isomerization of (1R,2S,7S,10S,11R,12S,13S)-2,6,6,10,12-pentamethylpentacyclo[10.2.1.01,10.02,7.011,13]pentadecane by fluorosulfonic acid

It has been shown that the opening of the cyclopropane ring in (1R, 2S, 7S, 10S, 11R, 12S, 13S)-2,6,6,10,12-pentamethylpentacyclo[10.2.1.0^1,10.0^2,7.0^11,13]pentadecane takes place under the action of fluorosulfonic acid at all three carbon-carbon bonds, but at low temperatures the main isomerization product is (1R, 2S, 7S, 10S, 12S, 13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadecan-13-ol, and at the ordinary temperature the main products are (1R, 2S, 7S, 11S, 12R, 13R)-2,6,6,11,13-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadeca-9-ene and (1S, 2R, 11S, 12R, 15R)-2,7,7,11,15-pentamethyltetracyclo[10.2.1.0^2,11.0^3,8]pentadeca-3(8)-ene.     

Terpenes in organic synthesis. 8. Synthesis of optically active (2R/S, 3S, 7R/S)-(-)-diprionyl acetate from (S)-(+)-3,7-dimethyl-1,6-octadiene

Conclusions A seven-stage synthesis has given optically active (2R/S, 3S, 7R/S)-2-acetoxy-3,7-dimethylpentadecane from the readily available (S)-(+)-3,7-dimethyl-1,6-octadiene, in an overall yield of 36%. The synthetic route utilizes all ten carbon atoms of the starting chiral diene.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1142–1146, May, 1988.     

The Synthesis of Novel S-, S,S-, S,S,S-, and N,S-Substituted Nitrodienes from Polyhalonitrodienes and Thiols

Abstract

The novel S-, S,S-, and S,S,S-substituted nitrobutadienes were synthesized from the reactions of 2-nitrobutadiene compounds with some thiols. The new N,S-substituted nitrobutadienes were obtained from the reaction of the mono-thiosubstituted butadienes with morpholine, thiomorpholine, homopiperazine, and piperazine derivatives. The structures of new compounds were determined by spectroscopic techniques.

GRAPHICAL ABSTRACT      

Cyclization and rearrangements of diterpenoids. IX. Isomerization of (1R,2S,7S,10S,11R,12S,13S)-2,6,6,10,12-pentamethylpentacyclo[10.2.1.01,10.02,7.011,13]pentadecane by fluorosulfonic acid

It has been shown that the opening of the cyclopropane ring in (1R, 2S, 7S, 10S, 11R, 12S, 13S)-2,6,6,10,12-pentamethylpentacyclo[10.2.1.0^1,10.0^2,7.0^11,13]pentadecane takes place under the action of fluorosulfonic acid at all three carbon-carbon bonds, but at low temperatures the main isomerization product is (1R, 2S, 7S, 10S, 12S, 13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadecan-13-ol, and at the ordinary temperature the main products are (1R, 2S, 7S, 11S, 12R, 13R)-2,6,6,11,13-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadeca-9-ene and (1S, 2R, 11S, 12R, 15R)-2,7,7,11,15-pentamethyltetracyclo[10.2.1.0^2,11.0^3,8]pentadeca-3(8)-ene.Institute of Chemistry, Moldavian SSR Academy of Sciences, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 497–500, July–August, 1989.     

Synthesis of dolichol-type (S)-hexa- and (S)-heptaprenols

(R)-1-Phenysulfonyl-2-methylbutan-4-ol has been used as starting material for the stepwise synthesis of the dolichol-related hexa- and heptaprenols (S)-3,7, 11,15,19,23-hexamethyltetraeicosa-6Z,10Z,14E,18E,22-pentaene-1-ol and (S)-3,7, 11,15,19,23,27-heptamethyloctaeicosa-6Z,10Z,14E,18E,22E,26-hexaen-1-ol.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2052–2056, September, 1989.     

Ring currents as probes of the aromaticity of inorganic monocycles : P5-, As5-, S2N2, S3N3-, S4N3+, S4N42+, S5N5+, S42+ and Se42+

Current-density maps were calculated by the ipsocentric CTOCD-DZ/6-311G** (CTOCD-DZ=continuous transformation of origin of current density-diamagnetic zero) approach for three sets of inorganic monocycles: S(4) (2+), Se(4) (2+), S(2)N(2), P(5) (-) and As(5) (-) with 6 pi electrons; S(3)N(3) (-), S(4)N(3) (+) and S(4)N(4) (2+) with 10 pi electrons; and S(5)N(5) (+) with 14 pi electrons. Ipsocentric orbital analysis was used to partition the currents into contributions from small groups of active electrons and to interpret the contributions in terms of symmetry- and energy-based selection rules. All nine systems were found to support diatropic pi currents, reinforced by sigma circulations in P(5) (-), As(5) (-), S(3)N(3) (-), S(4)N(3) (+), S(4)N(4) (2+) and S(5)N(5) (+), but opposed by them in S(4) (2+), Se(4) (2+) and S(2)N(2). The opposition of pi and sigma effects in the four-membered rings is compatible with height profiles of calculated NICS (nucleus-independent chemical shifts).     

Efficient and selective synthesis of (S,R,R,S,R,S)-4,6,8,10,16,18-hexamethyl-docosane via Zr-catalyzed asymmetric carboalumination of alkenes (ZACA reaction)

(S,R,R,S,R,S)-4,6,8,10,16,18-Hexamethyldocosane (1) was synthesized in 11% yield in 11 steps in the longest linear sequence from > or =98% pure (S)-beta-citronellal and 6 additional steps for the preparation of 11 in 23% yield from propene. Five of the six asymmetric carbon centers were generated catalytically and stereoselectively by the ZACA reaction (5 times), one lipase-catalyzed acetylation, and two chromatographic operations.     

Diastereoselective reaction of (1S,2S)-2-amino-1-(4-nitrophenyl)-1,3-propanediol with aromatic aldehydes. Synthesis of (1R,2R,4S,5S,8S)-2,8-diaryl-4-(4-nitrophenyl)-1-aza-3,7-dioxabicyclo[3.3.0]octanes

We have synthesized a series of (1R,2R,4S,5S,8S)-2,8-diaryl-4-(4-nitrophenyl)-1-aza-3,7-dioxabicyclo[3.3.0]octanes as a result of reaction of (1S,2S)-2-amino-1-(4-nitrophenyl)-1,3-propanediol with aromatic aldehydes. The structure of the compounds obtained was established on the basis of ¹H NMR data. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 757–763, May, 2006.     

A Study of S(3P2,1,0; 1D2; 1S0) Production in the 193 nm Photodissociation of CH3SH

The dynamics of S(³P_2,1,0; ¹D₂; ¹S₀) production from the 193 nm photodissociation of CH₃SH has been examined by 2+1 resonance-enhanced-multiphoton-ionization (REMPI) techniques. Using the rate equation scheme, we have rationalized the intensities of S(³P_2,1,0; ¹D₂; ¹S₀) observed according to the sequential two-photon dissociative pathways, (A): CH₃SH + hv (193 nm) → CH₃S + hv (193 nm) → S and (B): CH₃SH + hv (193 nm) → HS + hv (193 nm) → S, as the major mechanisms for S production. We have satisfactorily fitted the photodissociation laser power dependencies for S(³P) and S(¹D) produced from CH₃SH by invoking photodissociation cross sections and branching ratios S(³P)/S(¹D) for CH₃S and HS similar to those determined previously in the 193 nm photodissociation of CH₃SCH₃ and H₂S. This observation supports that the 193 nm photodissociation of CH₃S and HS prepared from CH₃SH yield predominantly S(^lD) and S(³P), similar to the cases for CH₃S prepared from CH₃SCH₃ and for HS prepared from H₂S, respectively. A small amount of S(¹S₀) observed from the 193 nm photodissociation of CH₃SH is attributed to pathway (B).     

Absence of Mn-centered oxidation in the S(2) --> S(3) transition: implications for the mechanism of photosynthetic water oxidation

A key question for the understanding of photosynthetic water oxidation is whether the four oxidizing equivalents necessary to oxidize water to dioxygen are accumulated on the four Mn ions of the oxygen-evolving complex (OEC), or whether some ligand-centered oxidations take place before the formation and release of dioxygen during the S(3) --> [S(4)] --> S(0) transition. Progress in instrumentation and flash sample preparation allowed us to apply Mn Kbeta X-ray emission spectroscopy (Kbeta XES) to this problem for the first time. The Kbeta XES results, in combination with Mn X-ray absorption near-edge structure (XANES) and electron paramagnetic resonance (EPR) data obtained from the same set of samples, show that the S(2) --> S(3) transition, in contrast to the S(0) --> S(1) and S(1) --> S(2) transitions, does not involve a Mn-centered oxidation. On the basis of new structural data from the S(3)-state, manganese mu-oxo bridge radical formation is proposed for the S(2) --> S(3) transition, and three possible mechanisms for the O-O bond formation are presented.     

Enhanced Electrocatalytic Water Oxidation by Interfacial Phase Transition and Photothermal Effect in Multiply Heterostructured Co9S8/Co3S4/Cu2S Nanohybrids

The rational design of advanced nanohybrids (NHs) with optimized interface electronic environment and rapid reaction kinetics is pivotal to electrocatalytic schedule. Herein, we developed a multiple heterogeneous Co₉S₈/Co₃S₄/Cu₂S nanoparticle in which Co₃S₄ germinates between Co₉S₈ and Cu₂S. Using high-angle annular-dark-field imaging and theoretical calculation, it was found that the integration of Co₉S₈ and Cu₂S tends to trigger the interface phase transition of Co₉S₈, leading to Co₃S₄ interlayer due to the low formation energy of Co₃S₄/Cu₂S (−7.61 eV) than Co₉S₈/Cu₂S (−5.86 eV). Such phase transition not only lowers the energy barrier of oxygen evolution reaction (OER, from 0.335 eV to 0.297 eV), but also increases charge carrier density (from 7.76×10¹⁴ to 2.09×10¹⁵ cm⁻³), and creates more active sites. Compared to Co₉S₈ and Cu₂S, the Co₉S₈/Co₃S₄/Cu₂S NHs also demonstrate notable photothermal effect that can heat the catalyst locally, offset the endothermic enthalpy change of OER, and promote carrier migrate, reaction intermediates adsorption/deprotonation to improve reaction kinetics. Profiting from these favorable factors, the Co₉S₈/Co₃S₄/Cu₂S catalyst only requires an OER overpotential of 181 mV and overall water splitting cell voltage of 1.43 V to driven 10 mA cm⁻² under the irradiation of near-infrared light, outperforming those without light irradiation and many reported Co-based catalysts.     

Coordination properties of the multifunctional S,N,S zwitterionic ligand EtNHC(S)Ph2PNPPh2C(S)NEt

The reaction of trialkylphoshanes and amino-phosphanes with isothiocyanates yields adducts containing the zwitterionic thioamidyl-phosphonium P⁺C(S)N^? functional group. Ligands containing this group were not previously studied, probably due to their instability towards dissociation, in the presence of metal species able to coordinate the P atom. The ligand EtNHC(S)Ph₂PNPPh₂C(S)NEt (HEtSNS) was obtained by reaction of Ph₂PNHPPh₂ with ethylisothiocyanate and proved to be very versatile: it can be protonated giving cation H₂EtSNS⁺ and deprotonated forming the dianion–cation EtSNS^?. HEtSNS and its derivatives behave as ligands showing five possible coordination fashions, S,N,S tridentate and S,S-bidentate (with a bite-angle varying from 180° to 90°), S-monodentate, S,S bridging and N,N,N interaction. Here we describe the coordination chemistry of HEtSNS, in particular towards Rh, Cu, Ag and Au, and some properties of its complexes which are still the only examples containing the P⁺C(S)N^? zwitterionic group.