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The Coral Red Kukri Snake Oligodon kheriensisis a rare and poorly known species; only a few specimens have been recorded so far since its first discovery in 1936. The species is endemic to the Himalayan tracts, previously reported only from northern India and Nepal. Here, we record and describe O. kheriensisfor the first time from Bangladesh as a third country report, thereby extending its distribution range. We also elaborate on details of its morphometry along with a discussion on its ecological niche, global distribution, intraspecific geomorphological variation, current conservation aspects, and possible conservation strategies.

A highly efficient, mild, and simple protocol is presented for the tandem OsO4-mediated oxidative cleavage/oxidative lactonization of alkenols to lactones. The protocol couples the OsO4-catalyzed oxidative cleavage of olefins with Oxone as the co-oxidant with the direct oxidation of aldehydes in alcoholic solvents to their corresponding esters.

A highly efficient, mild, and simple protocol is presented for the oxidation of aldehydes to carboxylic acids utilizing Oxone as the sole oxidant. Direct conversion of aldehydes in alcoholic solvents to their corresponding ester products is also reported. These reactions may prove to be valuable alternatives to traditional metal-mediated oxidations.

Monoamidation of 1,4-diaminobenzene with α-chiral carboxylic acids leads to a carrier strategy for absolute stereochemical determination with bis-zinc porphyrin tweezers by exciton-coupled circular dichroism (ECCD). The helicity induced in the porphyrin tweezers upon complexation with the derivatized carrier originates from the preferred conformation of the Ccarbonyl−Cchiral bond. Correct ECCD signs can be predicted by the rotamer that places the large group perpendicular to the carbonyl group with the small group facing the porphyrin.

Methylene-interrupted epoxydiols have multiple regiochemical routes for cyclization. The 5-exo process is the most prevalent under acidic conditions. However, the regioselectivity can be controlled by the appropriate choice of acid promoter and pendant groups adjacent to the epoxide. The 5-exo product is obtained exclusively without the presence of a carbocation-stabilizing pendant group. Alkenyl and thiophenyl groups adjacent to the epoxide alter the regioselectivity and enable access to the 5-endo tetrahydrofuran and 6-endo tetrahydropyran products.

18O-Labeled epoxides of trans-1,3-diphenylpropene oxide (tDPPO) and cis-9,10-epoxystearic acid were synthesized and used to determine the regioselectivity of sEH. The nucleophilic nature of sEH catalysis was demonstrated by comparing the enzymatic and nonenzymatic hydrolysis products of tDPPO. The results from single turnover experiments with greater or equal molar equivalents of sEH:substrate were consistent with the existence of a stable intermediate formed by a nucleophilic amino acid attacking the epoxide group. Tryptic digestion of sEH previously subjected to multiple turnovers with tDPPO in H2 18O resulted in the isolation and purification of a tryptic fragment containing Asp-333. Electrospray mass spectrometry of this fragment conclusively illustrated the incorporation of 180. After complete digestion of the latter peptide it was shown that Asp-333 of sEH exhibited an increased mass. The attack by Asp-333 initiates enzymatic activity, leading to the formation of an alpha-hydroxyacyl-enzyme intermediate. Hydrolysis of the acyl-enzyme occurs by the addition of an activated water to the carbonyl carbon of the ester bond, after which the resultant tetrahedral intermediate collapses, yielding the active enzyme and the diol product.

In order to investigate the involvement of amino acids in the catalytic mechanism of the soluble epoxide hydrolase, different mutants of the murine enzyme were produced using the baculovirus expression system. Our results are consistent with the involvement of Asp-333 and His-523 in a catalytic mechanism similar to that of other alpha/beta hydrolase fold enzymes. Mutation of His-263 to asparagine led to the loss of approximately half the specific activity compared to wild-type enzyme. When His-332 was replaced by asparagine, 96.7% of the specific activity was lost and mutation of the conserved His-523 to glutamine led to a more dramatic loss of 99.9% of the specific activity. No activity was detectable after the replacement of Asp-333 by serine. However, more than 20% of the wild-type activity was retained in an Asp-333-->Asn mutant produced in Spodoptera frugiperda cells. We purified, by affinity chromatography, the wild-type and the Asp-333-->Asn mutant enzymes produced in Trichoplusia ni cells. We labeled these enzymes by incubating them with the epoxide containing radiolabeled substrate juvenile hormone III (JH III). The purified Asp-333-->Asn mutant bound 6% of the substrate compared to the wild-type soluble epoxide hydrolase. The mutant also showed 8% of the specific activity of the wild-type. Preincubation of the purified Asp-333-->Asn mutant at 37 degrees C (pH 8), however, led to a complete recovery of activity and to a change of isoelectric point (pI), both of which are consistent with hydrolysis of Asn-333 to aspartic acid. This intramolecular hydrolysis of asparagine to aspartic acid may explain the activity observed in this mutant. Wild-type enzyme that had been radiolabeled with the substrate was digested with trypsin. Using reverse phase-high pressure liquid chromatography, we isolated four radiolabeled peptides of similar polarity. These peptides were not radiolabeled if the enzyme was preincubated with a selective competitive inhibitor of soluble epoxide hydrolase 4-fluorochalcone oxide. This strongly suggested that these peptides contained a catalytic amino acid. Each peptide was characterized with N-terminal amino acid sequencing and electrospray mass spectrometry. All four radiolabeled peptides contained overlapping sequences. The only aspartic acid present in all four peptides and conserved in all epoxide hydrolases was Asp-333. These peptides resulted from cleavage at different trypsin sites and the mass of each was consistent with the covalent linkage of Asp-333 to the substrate.