- Selective cleavage of tert-butyl esters in the presence of tert-butyl ethers. Application to the synthesis of tert-butoxy amino acids
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We report on the selective cleavage of tert-butyl esters in the presence of tert-butyl ether groups by using trimethylsilyl triflate. The method is especially useful for the synthesis of tert-butyl ethers of N-protected hydroxy amino acids which are valuable building blocks for peptide synthesis.
- Trzeciak, Arnold,Bannwarth, Willi
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- Deprotection of t-butyl esters of amino acid derivatives by nitric acid in dichloromethane
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The extension of the deprotection procedure of t-butylated carboxyl function using HNO3 in CH2Cl2 to a number of appropriately selected N-Z- derivatives of natural amino acid esters was investigated. The method was found to work effectively with alanine, phenylalanine, serine and the dipeptide aspartame, but the reagent brought about a number of unwanted transformations with tyrosine, methionine and tryptophan. Suitable protection of functions present in the latter ones allowed selective ester dealkylation, but tyrosine underwent unavoidable fast preliminary ring nitration. 2000 Elsevier Science Ltd.
- Strazzolini, Paolo,Scuccato, Massimo,Giumanini, Angelo G.
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p. 3625 - 3633
(2007/10/03)
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- Biosynthesis of Hyalodendrin and Didethiobis(methylthio)hyalodendrin, Sulphur-containing 2,5-Dioxopiperazines of the 3S,6S Series
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cyclo-(L-Phe-L-Ser) 8, a known biosynthetic precursor of the (3R,6R)-epidithiodioxopiperazine gliotoxin 4, was efficiently incorporated (42percent), in Hyalodendron sp. (FSC-601) cultures, into the 3S,6S metabolite didethiobis(methylthio)hyalodendrin (DBH) 7 without significant change in the 3H:14C ratio.None of the three diasteromers of cyclo-(L-Phe-L-Ser) was incorporated into DBH to any significant extent.The 13C label from cyclo-(L-Phe-L-Ser) was located, in the expected site, in DBH by 13C NMR spectroscopy.Gliotoxin derived in Gliocladium virens from the doubly labelled precursor 8 was degraded to locate, in similar manner, the 14C label.The N-methyl derivative 16 of cyclo-(L-Phe-L-Ser) was not incorporated detectably into either gliotoxin or DBH.Radioactivity from the doubly labelled, linear dipeptides 17 and 18, possible precursors for the cyclodipeptide 8, was incorporated with moderate efficiency into gliotoxin.However, the 3H:14C ratios for the dipeptides and the derived gliotoxin differd substantially, indicating that the peptides had undergone cleavage in the fungus before incorporation.
- Boente, Maria I. Pita,Kirby, Gordon W.,Patrick, Graham L.,Robins, David J.
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p. 1283 - 1290
(2007/10/02)
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