Total synthesis of the cyclopeptide alkaloid abyssenine A. Application of inter- and intramolecular copper-mediated coupling reactions in organic synthesis

The first total synthesis of the 15-membered ring cyclopeptide alkaloid abyssenine A 1 has been achieved with a longest linear sequence of 15 steps. Central to the synthetic approach was an efficient copper-mediated Ullmann coupling/Claisen rearrangement sequence allowing for both ipso and ortho functionalization of aromatic iodide 4. This sequence was used for the synthesis of the aromatic core. The synthetic utility of copper-catalyzed coupling reactions was further demonstrated to install the enamide with a concomitant straightforward macrocyclization starting from acyclic alpha-amido-omega-vinyl iodide 13.     

A convergent synthesis of the macrocyclic core of cytotrienins: application of RCM for macrocyclization

[reaction: see text] The asymmetric synthesis of the fully elaborated macrocyclic core of cytotrienins A-D, potent apoptosis-inducing agents, is described. Synthetic highlights include the construction of the aniline bond using a copper-mediated amidation and the use of a ring-closing metathesis (RCM) reaction to efficiently install the (E,E,E)-triene and simultaneously construct the macrocyclic lactam.     

Copper-catalyzed cyclization of iodo-tryptophans: a straightforward synthesis of pyrroloindoles

Pyrroloindoles are a key structural motif found in a wide number of biologically active alkaloids. Intramolecular copper-catalyzed coupling of readily accessible 2-iodo-tryptophan derivatives occurs in excellent yield, affording a wide range of polysubstituted, enantioenriched tetrahydropyrrolo[2,3- b]indoles. Diketopiperazines are also suitable substrates for this cyclization reaction, which affords a straightforward entry to tetra- to hepta-polycyclic systems.     

TMC-95A–D and analogues: Chemistry and biology

The proteasome regulates diverse intracellular processes, including cell-cycle progression, cell adhesion and migration, apoptosis and antigen presentation: selective inhibitors of the proteasome, therefore, have great therapeutic potential for the treatment of cancer. TMC-95A–D are unique natural products and represent a new class of noncovalent, reversible, and selective proteasome inhibitors with exceptionally strong bioactivity profiles and interesting structural properties. Significant recent advances in the syntheses of these natural products have led to intense interest in the development of related compounds as potential anticancer agents: the chemistry and biology of these natural products and analogues will be described in this review article.     

N-Cyanomethyl-β-chloro amines: chiral building blocks for the synthesis of azacrown ethers

(1R,2S)-Ephedrine and norephedrine derived N-cyanomethyl-β-chloro amines react with tri-, tetra- and penta-ethylene glycol to stereoselectively give the corresponding amino ethers. Further transformation into chiral monoaza 12-, 15- and 18-crown-4, -5 and -6 ethers was realized in three steps and good overall yields by: (i) mesylation, (ii) deprotection of the N-cyanomethyl group and (iii) intramolecular alkylation. Binding affinities of these azacrown ethers for alkali cations was studied by FAB-MS.