17360-47-3Relevant articles and documents
Solid phase reductive alkylation of secondary amines
Khan, Nawaz M.,Arumugam, Vijayalakshmi,Balasubramanian, Shankar
, p. 4819 - 4822 (1996)
Solid phase reductive alkylation of secondary amines has been carried out in excellent yields using borane-pyridine complex (BAP). Various aldehydes and ketones have been reacted with L-proline substituted on high-capacity Wang Resin.
SN1-type substitution reactions of N-protected β-hydroxytyrosine esters: Stereoselective synthesis of β-Aryl and β-alkyltyrosines
Wilcke, David,Herdtweck, Eberhardt,Bach, Thorsten
supporting information; experimental part, p. 1372 - 1382 (2012/07/30)
The title compounds were prepared by aldol reaction of anisaldehyde and the respective N,N-dibenzyl glycinates. Deprotection of the nitrogen atom with Pearlman's catalyst delivered the unprotected β-hydroxytyrosine esters, which were further N-protected as N,N-phthaloyl (Phth) and N- fluorenylmethylcarbonyloxy (Fmoc) derivatives. The Friedel-Crafts reaction with various arenes was studied employing these alcohols as electrophiles. It turned out that the facial diastereoselectivitiy depends on the nitrogen protecting group and on the ester group. The unprotected substrates (NH2) gave preferentially syn-products but the anti-selectivity increased when going from NHFmoc over NPhth to NBn2. If the ester substituent was varied the syn-preference increased in the order Me A model is suggested to explain the facial diastereoselectivity based on a conformationally locked benzylic cation intermediate. The reactions are preparatively useful for the N-unprotected isopropyl ester, which gave Friedel-Crafts alkylation products with good syn-selectivity (anti/syn=21:79 to 7:93), and for the N,N-dibenzyl-protected methyl ester, which led preferentially to anti-products (anti/syn=80:20 to >95:5). Upon acetylation of the latter compound to the respective acetate, Bi(OTf)3-catalyzed alkylation reactions became possible, in which silyl enol ethers served as nucleophiles. The respective alkylation products were obtained in high yield and with excellent anti-selectivitiy (anti/syn≥95:5). Copyright
Scope and limitation of the acid-catalyzed isomerization of Aib-containing thiopeptides
Breitenmoser, Roland A.,Heimgartner, Heinz
, p. 786 - 796 (2007/10/03)
The use of amino thio S-acids in the 'azirine/oxazolone method' and a novel isomerization led to Aib-containing endothiopeptides. With the aim of generalizing this method, a variety of Aib-containing dipeptide thioanilides have been prepared. By their treatment with ZnCl2 in AcOH, followed by HCl-saturated AcOH, the C=S group was shifted from the last to the penultimate amino acid in high yield and without epimerization. As this methodology is very useful for the specific introduction of a thioamide group, it was extended to Aib-containing tripeptides. In addition, it could be shown that a mechanism via spirocyclic intermediates (cf. Scheme 4) is most likely for this isomerization. To establish the proposed neighboring-group participation of the N-acyl group, model dipeptide thioanilides containing no N-terminal C=O group were synthesized. These derivatives did not undergo rearrangement.
