[Show abstract][Hide abstract] ABSTRACT: Friedländer reaction between methyl acetoacetate and 2,4-diaminobenzaldehyde provided quinoline 11. Subsequent tosylation, reduction, silylation, and then oxidation led to aldehyde 15. The latter was subjected to a Pictet–Spengler reaction with tryptophan methyl ester that yielded product 16, and then desilylation gave the lavendamycin analogue 17. This compound was oxidized by Dess–Martin periodinane, and the cyclized derivative 18 was obtained via a hemiaminal intermediate. The same sequence from 2,4-diamino-5-methoxybenzaldehyde or from (2,4-diaminophenyl)propan-3-one led to compounds 30 and 31, or 40 and 41, respectively.
[Show abstract][Hide abstract] ABSTRACT: Quinoline 12 was obtained by a Friedländer reaction from 2-aminobenzaldehyde and methyl acetoacetate. Reduction, silylation then oxidation provided compound 8a. A Pictet–Spengler reaction between the latter and tryptophan methyl ester yielded compound 14, then compound 7 by desilylation. Numerous attempts to prepare a cyclized derivative of this analogue of lavendamycin 7 by conventional ways failed. Fortunately, a good result was obtained via a hemiaminal intermediate and compound 21 was thus obtained in satisfactory yield. A conjugate addition occurred in the course of its reduction which led to compound 22. Biological tests were carried out with compound 7 and the conformationally restricted analogues 21 and 22.
Tetrahedron Letters - TETRAHEDRON LETT. 01/2007; 48(34):6014-6018.
[Show abstract][Hide abstract] ABSTRACT: Enantiomerically enriched cyclobutene compounds 13 and 24 are good precursors of several cyclobutane nucleoside analogs. The synthetic ways involve, in the key step, either hydroboration or dihydroxylation.
[Show abstract][Hide abstract] ABSTRACT: When compounds 3a and 3b were subjected to a Mitsunobu reaction with benzoylthymine, the expected substitution products were formed together with the regioisomers corresponding to benzyloxy group migrations.