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Galande Amit K. Spatola Arno F. 《International journal of peptide research and therapeutics》2001,8(3-5):247-251
Summary A series of disulfide bridged peptides were designed as potential inhibitors of protein-protein interactions. Following solid
phase synthesis, completely deprotected linear peptides were first oxidized to their disulfide analogs and then transformed
into their lanthionine equivalents via a base-assisted reaction in water. Peptides consisting of cystine bridges of lengthi, i+3, with and without discrimination of the chiral centers, were studied for this transformation. Lanthionine peptides were also
obtained directly from the reduced linear peptides under mild alkaline treatment, and the reaction proceeded via disulfide
bond formation. The extent of conversion of a disulfide bridge into its lanthionine counterpart varied according to the primary
sequence. Product characterization revealed diastereomeric lanthionine formation. The presence of D-amino acids, peptide conformation,
and/or position of the cystine bridge are among the factors determining the facility of this reaction. Elimination of the
backbone proton beta to the sulfur atom followed by intramolecular thiol Michael addition is the most likely mechanism for
this transformation. 相似文献
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Michel Randriaminahy Ludger Witte Arno Kunze Victor Wray Peter Proksch 《Biochemical Systematics and Ecology》1992,20(8):711-722
Five naturally occurring chromenes from the Asteraceae including the insecticidal compounds precocene II (1) and encecalin (2) were administered to last instar larvae of Spodoptera littoralis via the food or by topical contact. Metabolites formed and excreted via the frass were analysed by GC-MS and by direct comparison with reference compounds obtained by partial synthesis. In total 28 different metabolites were identified, many of them reported here for the first time. All metabolites detected originated from phase I reactions (most probably catalysed by Cytochrom P-450-dependent monooxygenases) by hydroxylation, demethylation or reduction of the parent chromenes. The resulting metabolites can be regarded as detoxification products based on previous structure-activity studies. The increased polarity of the metabolites will furthermore facilitate their excretion by the larvae compared to the more apolar parent chromenes. The largest number of metabolites (eight for each compound) was detected following oral treatment with precocene II and encecalin respectively. 3-Monool as well as 3,4-trans-diol derivatives predominated in the frass of larvae treated with the latter compounds whereas the 6-hydroxyethyl derivatives were the major metabolites of the other chromenes investigated. The patterns of metabolites originating from precocene II or encecalin were the same following oral application or topical treatment. 相似文献
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