RESUMEN
A review of the current status of the chemistry and biology of fostriecin (CI-920) is provided. Fostriecin is a structurally unique, naturally-occurring phosphate monoester that exhibits potent and efficacious antitumor activity. Initially it was suggested that its activity could be attributed to a direct, albeit weak, inhibition of the enzyme topoisomerase II. However, recent studies have shown that fostriecin inhibits the mitotic entry checkpoint through the much more potent and selective inhibition of protein phosphatase 2A (PP2A) and protein phosphatase 4 (PP4). In fact, it is the most selective small molecule inhibitor of a protein phosphatase disclosed to date. The contribution, if any, that topoisomerase II versus PP2A/PP4 inhibition makes to fostriecin's antitumor activity has not yet been fully defined. Initial phase I clinical trials with fostriecin never reached dose-limiting toxicity or therapeutic dose levels and were halted due to its storage instability and unpredictable chemical purity. Hence, the total synthesis of fostriecin has been pursued in order to confirm its structure and stereochemistry, to provide access to quantities of the pure natural product, and to access key partial structures or simplified/stable analogs. Several additional natural products have been isolated which contain similar structural features (phospholine, phoslactomycins, phosphazomycin, leustroducsins, sultriecin, and cytostatin), and some exhibit comparable biological properties.
Asunto(s)
Alquenos/síntesis química , Alquenos/farmacología , Antineoplásicos/síntesis química , Alquenos/química , Antineoplásicos/química , Antineoplásicos/farmacología , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Humanos , Fosfoproteínas Fosfatasas/antagonistas & inhibidores , Polienos , Proteína Fosfatasa 2 , Pironas , Relación Estructura-Actividad , Inhibidores de Topoisomerasa IIRESUMEN
A concise, efficient approach to the total synthesis of ningalin B (1) based on a heterocyclic azadiene Diels-Alder strategy (1,2,4,5-tetrazine-->1,2,-diazine-->pyrrole) ideally suited for construction of the densely functionalized pyrrole core found in the natural product is detailed. Examination of the natural product and a number of synthetic intermediates revealed that while lacking inherent cytotoxic activity, many reverse the multidrug-resistant (MDR) phenotype, resensitizing a human colon cancer cell line (HCT116/VM46) to vinblastine and doxorubicin at lower doses than the prototypical agent verapamil.