Recent Advances in Asymmetric Isocyanide-Based Multicomponent Reactions

Multicomponent reactions - opportunities for the pharmaceutical industry

Multicomponent reactions – reactions that combine three or more starting materials in one pot to give a single product that contains essentially all of the atoms of the reactants – offer many exciting opportunities for medicinal chemistry. Their most obvious application is in the drug discovery phase, where they can provide efficient access to large numbers of analogs for lead discovery or optimization. By contrast, the inherent 'greenness' of multicomponent reactions makes them of increasing importance in the sustainable production of pharmaceuticals. We will discuss recent advances in both fields as well as general drivers and barriers for the application of multicomponent reactions in a medicinal chemistry context.

The multicomponent approach to N-methyl peptides: total synthesis of antibacterial (-)-viridic acid and analogues

Two syntheses of natural viridic acid, an unusual triply N-methylated peptide with two anthranilate units, are presented. The first one is based on peptide-coupling strategies and affords the optically active natural product in 20% overall yield over six steps. A more economical approach with only four steps leads to the similarly active racemate by utilizing a Ugi four-component reaction (Ugi-4CR) as the key transformation. A small library of viridic acid analogues is readily available to provide first SAR insight. The biological activities of the natural product and its derivatives against the Gram-negative bacterium Aliivibrio fischeri were evaluated.

One-pot five-component synthesis of spirocyclopenta[b]chromene derivatives and their acid-catalyzed rearrangement

The reaction of the zwitterionic intermediate, generated in situ from either tert-butylisocyanide or cyclohexylisocyanide and acetylenedicarboxylates, with 3-cyanochromones is described, whereupon spirochromenofuran derivatives 5 or 6 were obtained in good yields. The subsequent acid-catalyzed rearrangement of the isolated 2-imino-spirochromenofurans 5 to 2-amino-spirochromenofurans 7 has also been studied. Rational mechanistic schemes for the formation of compounds 5, 6, and 7 are proposed. The structure elucidation of the products was accomplished by 1D and 2D NMR experiments and confirmed by X-ray crystallographic analysis. Full assignment of all (1)H and (13)C NMR chemical shifts has been unambiguously achieved with the aid of DFT/GIAO calculations.