(−)-15-Deoxyspergualin: A New and Efficient Enantioselective Synthesis Which Allows the Definitive Assignment of the Absolute Configuration

Targeted Imaging Agent to HSP70 Induced In Vivo

Heat shock protein expression can be induced by heat shock making it possible to artificially modulate their levels noninvasively in vivo in a spatially and temporally controlled manner. Here, we report the use of the major heat shock protein 70 (HSP70) as an inducible target by using the small molecule deoxyspergualin (DSG) conjugated to the near-infrared fluorophore (Cy5.5). We demonstrate that heat induction in the form of localized hyperthermia of normal tissue in living mice results in sufficient HSP70 overexpression for detection with DSG-Cy5.5 conjugate. This effect is dependent on total energy delivered and reaches maximum fluorescence signal in 6 to 8 hours post heat induction and declines over a period of up to 24 hours. These results suggest that DSG-Cy5.5 agent accumulates in tissue with elevated HSP70 by heat.

Unusual Amino Acids in Medicinal Chemistry

Unusual amino acids are fundamental building blocks of modern medicinal chemistry. The combination of readily functionalized amine and carboxyl groups attached to a chiral central core along with one or two potentially diverse side chains provides a unique three-dimensional structure with a high degree of functionality. This makes them invaluable as starting materials for syntheses of complex molecules, highly diverse elements for SAR campaigns, integral components of peptidomimetic drugs, and potential drugs on their own. This Perspective highlights the diversity of unnatural amino acid structures found in hit-to-lead and lead optimization campaigns and clinical stage and approved drugs, reflecting their increasingly important role in medicinal chemistry.

Improved synthesis of 15-deoxyspergualin analogs using the Ugi multi-component reaction

Spergualin is a natural product that exhibits immunosuppressive, anti-tumor and anti-bacterial activities. Its derivatives, such as 15-deoxyspergualin (15-DSG), have been clinically approved for acute allograft rejection. However, the reported syntheses are cumbersome (>10 steps) and they suffer from low overall yields (∼0.3% to 18%). Moreover, spergualin and its derivatives are chemically unstable and rapidly hydrolyzed in aqueous buffer. Here, we have re-explored these issues and report a modified synthetic route with significantly improved overall yield (∼31% to 47%). The key transformation is a microwave-accelerated Ugi multi-component reaction that is used to generate the peptoid core in a single step. Using the products of this route, we found that modifications of the hemiaminal significantly increased chemical stability. Thus, we anticipate that this synthetic route will improve access to biologically active 15-DSG derivatives.

New beta-strand macrocyclic peptidomimetic analogues containing alpha-(O-, S- or NH-)aryl substituted glycine residues: synthesis, chemical and enzymatic properties

In so much as bis-macrocyclic peptidomimetics have been recognized as high affinity substrates for HIV-1 protease, we were interested in the design and synthesis of new bis-macrocyclic bioisosteric analogues whose general structure is displayed on Fig. 2. The structures of these new analogues are characterized by the specific replacement of the methylene of the benzyl group directly attached to the N-acyl glycine residue in the original molecule 1, by its main bioisosteres, i.e. O-, S- and NH-aryl groups. Knowing that an intermediate in which an heteroatomic aryl group is directly linked to a free amine glycine residue is not stable, we developed an original synthetic pathway which involved the coupling of a specific side chain to the exocyclic carboxylic acid function, followed by an elegant oxidation-nucleophilic substitution Steglich-type reaction. Analogues 2a-d were then submitted to chemical and enzymatic hydrolysis. We demonstrated that, as expected, the specific cleavage of the exocyclic N-acyl bond led to the release of aryl moieties (phenol, thiophenol and aniline species). These chemical and enzymatic stability studies brought to light the biological potential of such macrocyclic analogues in infected cells.