2, 4-Dimethyl -5 -nitrofuran -3 -carboxylic acid and its derivatives

It is found that 2, 4-dimethyl-5-nitrofuran-3-carboxylic acid and its methyl ester can give comparatively stable anionic groups, which are prepared electrochemically and investigated by EPR. Their lives (80–100 sec) are 4- 5 times greater than the lives of other anionic groups of the 5-nitrofuran series previously studied. Starting from 2, 4-dimethyl-5-nitrofuran-3-carboxylic acid and 2, 4-dimethylfuran-3-carboxylic acid, two new semisynthetic penicillins are prepared, with activities basically extending to Gram-positive microorganisms, including forms of staphylcocci resistant to benzylpenicillin. Introduction of the nitro group into the furan ring increases the stability of penicillin to acid 79-fold. Low toxicity penicillins are synthesized (LD₅₀ 1000–1500 mg/kg).     

Analogs of pyrimidine nucleosides

N₁-(-Tetrahydrofuranyl)- and N₁-(-tetrahydropyranyl)uracils and the corresponding 6-azauracils have been obtained by the condensation of bistrimethylsilyl derivatives of uracils and 6-azauracils with-chlorotetrahydrofuran and-chlorotetrahydropyran. The superiority of the silyl method over the mercury method used previously has been demonstrated.For part III, see [9].     

An automated large volume on-column injection technique for capillary gas chromatography

Automated large volume (25-200 μl) on-column injections into a gas chromatograph with a capillary column were successfully performed by coupling a retention gap technique with an air actuated rotary valve. The linearity, injection precision, and carryover were evaluated. Slight boiling point discrimination was observed. This technique is compatible with commonly used chromatographic detectors (FID, ECD, MS) and conditions, while requiring very little instrument modification. The work is directed at the eventual reduction of manpower and turnaround time for sample collection and extraction, and Kuderna-Danish concentration when dealing with methods similar to EPA 625.     

Über die Reaktion des käfigartigen Kieselsäurederivats [(CH3)2HSi]8Si8O20 mit ungesättigten organischen Verbindungen

Reaction of the Cage-like Silicic Acid Derivative [(CH₃)₂HSi]₈Si₈O₂₀ with Unsaturated Organic Compounds By ²⁹Si, ¹H, and ¹³C NMR investigations were shown that the eight HSi?groups of the double four-ring silicic acid derivative [(CH₃)₂HSi]₈Si₈O₂₀ react with the following unsaturated compounds: vinylcyclohexene, allyl glycidyl ether, methyl methacrylate, octadecene-1, and styrene. The resulting oily products are soluble in organic solvents. The compounds were characterized by the chemical shifts of the ²⁹Si, ¹H, and ¹³C NMR signals. Their formulae are [C₆H₉(CH₂)₂Si(CH₃)₂]₈Si₈O₂₀, [CH₃OOCCH(CH₃)CH₂Si(CH₃)₂]₈Si₈O₂₀, [CH₃(CH₂)₁₇Si(CH₃)₂]₈Si₈O₂₀ and [C₆H₅(CH₂)₂Si(CH₃)₂]₈Si₈O₂₀, and [C₆H₅CH(CH₃)Si(CH₃)₂]₈ Si₈O₂₀, respectively. Mainly the addition reactions do not follow the Markovnikov rule.     

The charge-transfer character of the S0 --> S2 transition in the carotenoid peridinin is revealed by Stark spectroscopy

Peridinin, the carotenoid in the peridinin chlorophyll a protein (PCP), was studied by Stark (electroabsorption) spectroscopy to determine the change in electrostatic properties produced on excitation within the absorption band, in methyl tetrahydrofuran (MeTHF) versus ethylene glycol (EG), at 77 K. Strikingly, a large change in the permanent dipole moment (|Deltamu|) was found between the ground state, S(0) (1(1)A(g)(-)), and the Franck-Condon region of the S(2) (1(1)B(u)(+)) excited state, in both MeTHF (22 D) and EG (approximately 27 D), thus revealing the previously unknown charge transfer (CT) character of this pi-pi transition in peridinin. Such a large |Deltamu| produced on excitation, we suggest, facilitates the bending of the lactone moiety, toward which charge transfer occurs, and the subsequent formation of the previously identified intramolecular CT (ICT) state at lower energy. This unexpectedly large S(2) dipole moment, which has not been predicted even from high-level electronic structure calculations, is supported by calculating the shift of the peridinin absorption band as a function of solvent polarity, using the experimentally derived result. Overall, the photoinduced charge transfer uncovered here is expected to affect the excited-state reactivity of peridinin and, within the protein, be important for efficient energy transfer from the carotenoid S(2) and S(1)/ICT states to the chlorophylls in PCP.     

N‐Functionalized Ferrocenes: Subvalent Group XIV Element Chlorides and tert‐Butyllithium‐Induced C−C Bond Cleavage under Mild Conditions

The ferrocene derivative (η⁵‐Cp)Fe{η⁵‐C₅H₃‐1‐(ArNCH)‐2‐(CH₂NMe₂)} ( 1 ; Ar=2,6‐iPr₂C₆H₃)) reacts diastereoselectively with LiR by carbolithiation and subsequent hydrolysis to give (η⁵‐Cp)Fe{η⁵‐C₅H₃‐1‐(ArHNCHR)‐2‐(CH₂NMe₂)} ( 3 : R=tBu; 4 : R=Ph; 5 : R=Me) in high yields. For R=tBu, the organolithium derivative (η⁵‐Cp)Fe{η⁵‐C₅H₃‐1‐(ArLiNCHR)‐2‐(CH₂NMe₂)} ( 2 ) was isolated. Compound 2 reacts with GeCl₂?dioxane and SnCl₂ to give the metallylene amide chlorides (η⁵‐Cp)Fe{η⁵‐C₅H₃‐1‐(ArMNCHtBu)‐2‐(CH₂NMe₂)} 6 (M=GeCl) and 7 (M=SnCl), respectively, which each contain three stereogenic centers. The potential of 7 as a ligand in transition‐metal chemistry is demonstrated by formation of its complex (η⁵‐Cp)Fe{η⁵‐C₅H₃‐1‐(ArMNCHtBu)‐2‐(CH₂NMe₂)} [ 9 , M= Sn(Cl)W(CO)₅]. Treatment of 3 with tert‐butyllithium at room temperature causes an unprecedented carbon–carbon bond cleavage whereas under kinetic control, lithiation at the Cp‐3 position takes place, which leads to the isolation of (η⁵‐Cp)Fe{η⁵‐C₅H₃‐1‐(ArHNCHtBu)‐2‐(CH₂NMe₂)‐3‐SiMe₃} ( 10 ).     

Synthesis of novel 2-azabicyclo[2.2.0]- and [2.1.1]hexanols

Methyl- and phenyl-substituted N-(ethoxycarbonyl)-2-azabicyclo[2.2.0]hex-5-enes 6 were reacted with NBS in wet DMSO to afford bromohydrins. Mixtures of unrearranged 6-exo-bromo-5-endo-hydroxy-2-azabicyclo[2.2.0]hexanes 7a,b and rearranged 5-anti-bromo-6-anti-hydroxy-2-azabicyclo[2.1.1]hexanes 8a,b were formed stereoselectively from the parent alkene 6a and 4-methyl alkene 6b. The 5-methyl alkene 6c affords only unrearranged bromohydrin 7c and dibromohydrin 9. By contrast, solely rearranged 3-endo-substituted-2-azabicyclo[2.1.1]hexane bromohydrins 8d-f result from additions to 3-endo-methyl alkene 6d, 3-endo-4-dimethyl alkene 6e, and 3-endo-phenyl alkene 6f. As an alternative route to bromohydrins, the parent 5,6-exo-epoxide 10a and 5-endo-methyl-5,6-exo-epoxide 10b were ring opened with bromine/triphenylphosphine to afford unrearranged 5-endo-bromo-6-exo-hydroxy-2-azabicyclo[2.2.0]hexanes 11a,b, while the 3-endo-methyl epoxide 10c afforded solely the rearranged 5-anti-bromo-6-anti-hydroxy-3-exo-methyl-2-azabicyclo[2.1.1]hexane isomer 8g. Tributyltin hydride reduction of bromohydrins 7a,b and 11a afforded novel 2-azabicyclo[2.2.0]hexan-5-ols 13a,b and -6-ol 14, and bromohydrins 8a,b, 8d-g afforded new 2-azabicyclo[2.1.1]-hexan-5-ols 15a,b and 15d-g.