Asymmetric Synthesis Of 3-aryl-2,3-diamino Acids

Partâ… .2,3-Diamino Acids:Biological Activities and Synthetic ApproachesOptically active 2,3-diamino acids are an important class of compounds due to their presence in a variety of peptide antibiotics,antifungal dipeptides,and other biologically active compounds.Additionally,aside from the above considerations,two vicinal chiral centers has also represented a challenge for synthetic organic chemists, especially the synthesis of enantiopure materials.Therefore,the aim of this part is to provide a general view of the existing methodology for the synthesis of 2,3-diamino acids and their simple derivatives,esters or amides.Partâ…¡.Asymmetric synthesis of 2,3-diamino acidsA novel and convenient route to the asymmetric synthesis of 2,3-diamino acids via Mannich reactions of iminolactones with N-protected imines has been achieved in good yields(up to 95%)and high diastereoselectivity(dr＞99:1).Hydrolysis of the Mannich adducts under acidic conditions furnished the desired 3-aryl-2,3-diaminopropanoic acids in good yields(up to 85%)with excellent enantiomeric excesses(99%ee).All of the new compounds were characterized by ¹H NMR,¹³C NMR and HRMS.Partâ…¢.Synthesis of New S-nucleosides of 5-(4-Pyridyl)-4-aryl-4H-1,2,4-triazole-3-thiols1,2,4-triazole derivatives have a broad spectrum of biological activities such as anti-inflammatory,antiviral,anticonvulsant,antitumor,antidepressant,antifungal and antimicrobial activity.Direct glycosylation of 5-(4-Pyridyl)-4-aryl-4H-1,2,4-triazole-3-thiols in the presence of potassium hydroxide followed by deacetylation using dry ammonia in methanol gave the corresponding 3-S-(β-D-glucopyranosyl)-5-(4-pyridyl)-4-aryl-4H-1,2,4-triazoles in good yields.All the compounds were fully characterized by means of ^H NMR,¹³C NMR spectra and elemental analyses.Partâ…£.Synthesis of 2-substituted amino-6-methyl-5-oxo-4-n-butyl-4,5-dihydro-1,2,4 -triazolo[1,5-a]pyrimidine derivatives.2-amino-6-methyl-5-oxo-4,5-dihydro-1,2,4-triazolo[1,5-a]pyrimidine was synthesized from 2-bromopropionic acid methyl ester,α,α-dichloromethyl methyl ether and guanazole via condensation and cyclization reactions.An attempt to improve its solubility in organic solvents was achieved by the nucleophilic substitution with 1-bromobutane to give 2-amino-6-methyl-5-oxo-4-n-butyl-4,5-dihydro-1,2,4-triazolo[1,5-a]pyrimidine in good yield.Finally,a series of 2-substituted amino-6-methyl-5-oxo-4-n-butyl-4,5-dihydro-1,2,4-triazolo[1,5-a]pyrimidine having potential emetic activity properties were obtained by ugi multi-component reaction. The structures of these compounds were confirmed by MS,¹H and ¹³C NMR spectra and elemental analysis.