1. Boc-Cys(Npys)-OH (BCNP): an appropriate reagent for the identification of T cell epitopes in cystine and/or cysteine-containing proteins
G Mourier, B Maillère, J Cotton, M Hervé, S Leroy, M Léonetti, A Ménez J Immunol Methods. 1994 May 2;171(1):65-71. doi: 10.1016/0022-1759(94)90229-1.
Some T cell epitopes become inactive when their thiols are blocked with various irreversible reagents (Régnier-Vigouroux, 1988; Maillère, 1992; Maillère et al., 1993). Blocking protein and peptide thiols with BCNP (Boc-Cys(Npys)-OH) constitutes a most appropriate strategy when searching for thiol-containing T cell epitopes. Free cysteines can thus be readily transformed into disulphide-like moieties which not only resist undesirable oxidative reactions but which also remain susceptible to reduction by antigen presenting cells, a prerequisite for the activity of thiol-dependent T cell epitopes. We describe the use of this reagent in a study of the intact disulphide-rich protein, toxin alpha from Naja nigricollis, and also two disulphide-containing toxin fragments.
3. Synthetic studies on (-)-lemonomycin: an efficient asymmetric synthesis of lemonomycinone amide
Yan-Chao Wu, Guillaume Bernadat, Géraldine Masson, Cédric Couturier, Thierry Schlama, Jieping Zhu J Org Chem. 2009 Mar 6;74(5):2046-52. doi: 10.1021/jo8027449.
Asymmetric synthesis of lemonomycinone amide (2) was accomplished from readily accessible starting materials. Enantioselective alkylation of N-(diphenylmethylene)glycine tert-butyl ester (11) by 5-tert-butyldimethylsilyloxy-2,4-dimethoxy-3-methylbenzyl bromide (10) in the presence of Corey-Lygo's phase transfer catalyst [O-(9)-ally-N-(9'-anthracenylmethyl) cinchonidium bromide, 0.1 equiv] afforded, after chemoselective hydrolysis of the imine function (THF/H(2)O/AcOH), the substituted l-tert-butyl phenylalanate 13 in 85% yield. A Pictet-Spengler reaction of 14 with benzyloxyacetaldehyde (15) provided the 1,3-cis-disubstituted tetrahydroisoquinoline 16 in 85% yield as a single diastereomer. Coupling of hindered secondary amine 16 with amino acid 9 was accomplished under carefully controlled conditions to furnish the amide 22, which was in turn converted to hemiaminal 24. A hafnium triflate catalyzed conversion of hemiaminal to alpha-amino thioether followed by a silver tetrafluoroborate promoted intramolecular Mannich reaction of 26 afforded the tetracycle 27 in excellent overall yields. Debenzylation of 27 [Pd(OH)(2), H(2), MeOH, 0 degrees C], removal of N-Boc function (aqueous 3 N HCl, MeOH/H(2)O), and oxidation of hydroquinone to quinone [(NH(4))(2)Ce(NO(3))(6), H(2)O, rt] afforded the lemonomycinone amide 2 in 76% yield over three steps.
