Recent advances in asymmetric multicomponent reactions (AMCRs)

Asymmetric multicomponent reactions (AMCRs) include the reaction of three or more reactants simultaneously to produce chiral products that they have some advantages containing simple procedures, saving time and energy, and being environmentally friendly processes. AMCRs have seen much development and their potent synthetic approaches are discussed in this review.     

‘Bis-ornithine’ (2,2-bis(aminopropyl)glycine): a new tetravalent template for assembling different functional peptides

Synthesis of bis-ornithine, a new C^α,α-disubstituted α-amino acid bearing orthogonally protected α and δ amine groups is reported. Bis-ornithine (bisOrn) and dipeptides containing bis-ornithine have been synthesized in solution up to multigram scale. As a first example, one of these compounds Boc-βAla-bisOrn(Alloc)₂-OH has been attached to a solid support and used as template for the synthesis of a symmetrical assemblage of peptides.     

An Efficient and Economical Method for the Preparation of Fmoc-Argω,ω'(Boc)2-OH

The arginine derivative Fmoc‐Arg^ω,ω′(Boc)₂‐OH has been prepared in perfect yield starting from Fmoc‐Orn·HCl and N,N′‐di‐Boc‐N′′‐triflyguanidine with the presence of diisopropylethylamine (DIEA). This work provides an efficient and economical method for the preparation of this compound.     

Synthesis of ‘difficult’ peptide sequences: application of a depsipeptide technique to the Jung-Redemann 10- and 26-mers and the amyloid peptide Aβ(1-42)

Recently a 26-mer peptide 1 incorporating Ser and Thr was described as a ‘difficult’ sequence that could not be synthesized by standard methods. If the first Ser residue was used to incorporate a depsipeptide unit, the resulting hybrid was readily assembled. The 26-mer ester was then converted to the native peptide by an O→N acyl shift. The technique may be general for other systems containing appropriate Ser and Thr units and was demonstrated here for the case of the amyloid peptide Aβ(1-42).     

Synthesis of cytisine derivatives of coumarins

New substituted 4-chloromethylcoumarins that were used as alkylating agents to modify cytisine were synthesized by Pechmann condensation. A series of 4-(12-cytisylmethyl)coumarins containing pharmacophores of the natural heterocycles coumarin and cytisine in a single molecule was prepared. The alkylation gave the best results if diisopropylethylamine was used as the base. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 485–488, September–October, 2007.     

Organic Base‐Catalyzed Stereoselective Isomerizations of 4‐Hydroxy‐4‐phenyl‐but‐2‐ynoic Acid Methyl Ester to (E)‐ and (Z)‐4‐Oxo‐4‐phenyl‐but‐2‐enoic Acid Methyl Esters

We have developed a 1,4‐diazabicyclo[2.2.2]octane (DABCO)‐catalyzed isomerization of 4‐hydroxy‐4‐phenyl‐but‐2‐ynoic acid methyl ester to (E)‐4‐oxo‐4‐phenyl‐but‐2‐enoic acid methyl ester and an N,N‐diisopropylethylamine‐catalyzed isomerization of the same substrate to (Z)‐4‐oxo‐4‐phenyl‐but‐2‐enoic acid methyl ester.