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all the final results of the syntheses could be predicted based on the simple modelexperiment. Until recently several chiral coupling reagents 2 were prepared usingstrychnine, brucine or other alkaloids as chiral auxiliary. Their effectiveness was proven inthe synthesis of amides, esters and dipeptides with fully predictable configuration and eereaching 86-99% [1]. Unresolved, however, remained access to both enantiomeric productsof the condensation, because chiral auxiliaries used in the studies were accessible only insingle enantiomeric form.Herein both enantiomeric forms of the enantioselective coupling reagent 7R and 7Swere prepared (Figure 2) in high yield by the treatment of tetrafluoroborates of methylesters of R and/or S N-methylproline respectively with 2-chloro-4,6-disubstituted-1,3,5-triazine in the presence of sodium bicarbonate [2].ClClBF - OBF -4 4 ON NN NOMeOOOMeN + N + MeO N OO N OOMeOMeMeN NN + N + NaHCO MeMeN N3 BF -NaHCO4-3O N OHH BF4O N O7R6R6S7SFig. 2. Synthesis of a pair of enantioselective coupling reagents 7S and 7R.Reagents 7R and 7S were found stable at room temperature. Both of them yielded with4-methoxybenzoic acid appropriate active ester 4, identical with a product obtained withN-methyl-N-(4,6-dimethoxy-1,3,5-triazin-2-yl)morpholinium tetrafluoroborate (3).Table 1. Synthesis of Z-Ala-Gly-OMe from rac-Z-Ala-OH using enantioselectiveN-triazinylammonium salts derived from L and D prolineEntry coupling reagent Yield [%] configuration D/L [%]1 7S (from L-Pro) 67 D 79/212 7R (from D-Pro) 65 L 25/75It has been found that activation of rac-Z-Ala-OH with 7S or 7R followed by coupling withH-Gly-OMe gave enantiomerically enriched dipeptide Z-Ala-Gly-OMe (Table 1).Determination of enantiomeric excess and configuration of dipeptide by chromatographicmethod using standard procedure GC with capillary ChirasilVal column confirmed theopposite configurational preferences of both coupling reagents. It was found that reagent7S privileged activation of Z-D-Ala-OH, but in the presence of 7R activation of Z-L-Ala-OH is favored.AcknowledgmentsThis work was supported by Ministry of Science and Higher Education, Grant 6/PMPP/U/30-09.08/E-370/2009.References1. (a) Kolesinska, B., Kaminski, Z.J. Org. Lett. 11, 765-768 (2009); (b) Kolesinska, B., Kasperowicz,K., Sochacki, M., Mazur, A., Jankowski, S., Kaminski, Z.J. Tetrahedron Lett. 51, 20-22 (2010).2. (a) Kolesinska, B., Kaminski, Z.J. Polish Pat. Appl. P-38476 from 04.02. 2008; (b) Kaminski, Z.J.,Kolesinska, B. Patent EPO 09001796,3-1211, priority PL/04.02.08/ PLA 384377608. from29.04.2009.123