Total synthesis of the phytotoxic stagonolides A and B

The chemo-enzymatic and covergent synthesis of stagonolide B and the synthesis of stagonolide A, a phytotoxic 10-membered lactone have been achieved starting from d-ribose with overall yields of 25% and 8.7%, respectively. The synthesis contained simple steps in developing three centers’ key intermediates, namely the enzymatic (Novozyme-435) resolution of a propargylic alcohol followed by macrolactonization and RCM.     

Sustainability Evaluation of Immobilized Acid-Adapted Microalgal Technology in Acid Mine Drainage Remediation following Emergy and Carbon Footprint Analysis

Sustainability evaluation of wastewater treatment helps to reduce greenhouse gas emissions, as it emphasizes the development of green technologies and optimum resource use rather than the end-of-pipe treatment. The conventional approaches for treating acid mine drainages (AMDs) are efficient; however, they need enormous amounts of energy, making them less sustainable and causing greater environmental concern. We recently demonstrated the potential of immobilized acid-adapted microalgal technology for AMD remediation. Here, this novel approach has been evaluated following emergy and carbon footprint analysis for its sustainability in AMD treatment. Our results showed that imported energy inputs contributed significantly (>90%) to the overall emergy and were much lower than in passive and active treatment systems. The microalgal treatment required 2–15 times more renewable inputs than the other two treatment systems. Additionally, the emergy indices indicated higher environmental loading ratio and lower per cent renewability, suggesting the need for adequate renewable inputs in the immobilized microalgal system. The emergy yield ratio for biodiesel production from the microalgal biomass after AMD treatment was >1.0, which indicates a better emergy return on total emergy spent. Based on greenhouse gas emissions, carbon footprint analysis (CFA), was performed using default emission factors, in accordance with the IPCC standards and the National Greenhouse Energy Reporting (NGER) program of Australia. Interestingly, CFA of acid-adapted microalgal technology revealed significant greenhouse gas emissions due to usage of various construction materials as per IPCC, while SCOPE 2 emissions from purchased electricity were evident as per NGER. Our findings indicate that the immobilized microalgal technology is highly sustainable in AMD treatment, and its potential could be realized further by including solar energy into the overall treatment system.     

Measurement of K X-ray intensity ratios in Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn employing carbon and nitrogen projectiles – VTT method

A method is suggested to effect the self absorption correction in a different way to estimate the K X-ray intensity ratios particularly when heavy ions are used as projectiles. Employing this method, the K_β/K_α intensity ratios are measured in some 3d shell elements by using Carbon and Nitrogen ions as exciting agents. The K_β/K_α intensity ratios thus obtained in the present work are compared with the intensity ratios due to some previous authors and also with Scofield theoretical values. Received 14 August 2000 and Received in final form 3 January 2001     

The probable iodine molecular lasers in the violet and ultraviolet regions

Iodine when excited in the presence of argon shows three band systems in the regions 4420–4000 Å., 3,460–3015 Å. and 2785–2731 Å. all of which involve O _u ^Emphasis>+ (³π _u ) state at 15642 cm.^?1 as the common lower state. It is pointed out in this article that the transitions involving the first two band systems are suitable for laser action as these transitions are very strong and as their common lower state gets efficiently flushed out due to the crossing or touching of a O _u ^Emphasis>? repulsive state while a continued high frequency discharge through a mixture of iodine and argon would keep the upper state populated all the time. Tuning of the interferometer system is expected to make this laser action possible in a wide range of frequencies.     

Liquid chromatographic separation and determination of aromatic sulfonates in an aquatic environment using a photodiode array and electrospray ionization-mass spectrometer as detectors.

A simple and rapid method involving high-performance liquid chromatographic separation, followed by photodiode array (PDA) and electrospray ionization-mass spectrometric (ESI-MS) detection of aromatic sulfonates in waste-water effluents of industrial units producing optical whitening agents, has been developed. The separation was achieved on a reversed-phase Hypersil C18 column using gradient elution of a mobile phase consisting of 0.05 M ammonium formate-methanol with decreasing concentration of the buffer at room temperature. The minimum detection limits were determined to be in the range of 0.2 - 1.8 x 10(-9) g using PDA and ESI-MS detectors.     

Resonance series of Br2 in the vacuum ultraviolet

A high-resolution resonance fluorescence spectrum of bromine excited by an electrical discharge in the region 1500–2100 Å was photographed on a 10.7-m concave grating vacuum spectrograph. Twelve resonance doublet series excited by four bromine atomic resonance lines were identified and analyzed. All doublet series have the ground state of ^79,81Br₂ as the lower electronic state. The vibrational numbers of these doublets corresponding to this state vary from 0 to 76. Rotational constants are obtained by least-squares fitting of the doublet separations, and the vibrational constants by least-squares analysis of vibrational term values. Probable assignments for the upper electronic state(s) of the transitions involved were suggested.     

A highly chemoselective Boc protection of amines using sulfonic-acid-functionalized silica as an efficient heterogeneous recyclable catalyst

A facile and versatile method for the chemoselective Boc protection of amines has been developed by a treatment with (Boc)₂O in the presence of sulfonic-acid-functionalized silica as a catalyst. The method is general for the preparation of N-Boc derivatives of aliphatic (acyclic and cyclic), aromatic, and heteroaromatic amines; primary and secondary amines; aminols, amino-esters; and sulfonamides. The catalyst works under heterogeneous conditions and can be recycled.     

Isoaurostatin: total synthesis and structural revision

Isoaurostatin, a topoisomerase I inhibitor isolated from Thermomonospora alba has been synthesized for the first time from 2,4-dihydroxyacetophenone via 6-methoxybenzo-2(3H)-furanone in five steps. The E-isomer was converted into Z-isomer, but spectroscopic data of either of these two isomers did not match with those of the natural product. The structure of isoaurostatin has been revised to a known isoflavone, daidzein (2), based on careful analysis of spectroscopic data.