Cultivation and extraction of the
fungus Talaromyces stipitatus led to the isolation
of five new oxyphenalenone–amino acid
hybrids, which were named talauxins E, Q, V, L, and I based on the
corresponding one-letter amino acid codes, along with their putative
biosynthetic precursor, duclauxin. The rapid reaction of duclauxin
with amino acids to produce talauxins was demonstrated in vitro and
exploited to generate a small library of natural and unnatural talauxins.
Talauxin V was shown to undergo spontaneous elimination of methyl
acetate to yield the corresponding neoclauxin scaffold. This process
was modeled using density functional theory calculations, revealing
a dramatic change in conformation resulting from the syn elimination of methyl acetate.
Chemical investigation of an Australian fungus, Aspergillus banksianus, led to the isolation of the major metabolite banksialactone A (1), eight new isochromanones, banksialactones B-I (2-9), two new isocoumarins, banksiamarins A and B (10 and 11), and the reported compounds, clearanol I (12), dothideomynone A (13), questin (14), and endocrocin (15). The structures of 1-11 were established by NMR spectroscopic data analysis, and the absolute configurations were determined from optical rotations and ECD spectra in conjunction with TD-DFT calculations. The secondary metabolite profile of A. banksianus is unusual, with the 11 most abundant metabolites belonging to a single isochromanone class. Conjugation of 1 with endocrocin, 5-methylorsellinic acid, 3,5-dimethylorsellinic acid, mercaptolactic acid, and an unknown methylthio source gave rise to five unprecedented biosynthetic hybrids, 5-9. The isolated compounds were tested for cytotoxicity, antibacterial, and antifungal activities, with hybrid metabolites 7-9 displaying weak cytotoxic and antibiotic activities.
The equivalent oxide thickness ͑EOT͒ of high-k n-channel metal oxide semiconductor ͑NMOS͒ transistors was scaled using 3 methods, ͑i͒ reduction of the bottom interfacial layer ͑BIL͒ using NH 3 interface engineering, (ii) thickness reduction of the HfO 2 dielectric, and (iii) use of metal gate electrodes to minimize top interfacial growth formation and polysilicon depletion. NMOS transistors fabricated using these methods demonstrate 0.72 nm EOT using the NH 3 BIL with scaled HfO 2 /metal gates and 0.81 nm EOT using the O 3 BIL with scaled HfO 2 /metal gates. Charge pumping, mobility, and device performance results of these high-k NMOS transistors is discussed.
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