Search

We designed and synthesized two novel series of azapodophyllotoxin analogues as potential antivascular agents. A linker was inserted between the trimethoxyphenyl ring E and the tetracyclic ABCD moiety of the 4-aza-1,2-didehydropodophyllotoxins. In the first series, the linker enables free rotation between the two moieties; in the second series, conformational restriction of the E nucleus was considered. We have identified several new compounds with inhibitory activity toward tubulin polymerization similar to that of CA-4 and colchicine, while displaying low cytotoxic activity against normal and/or cancer cells. An aminologue and a methylenic analogue were shown to disrupt endothelial cell cords on Matrigel at subtoxic concentrations, and an original assay of drug washout allowed us to demonstrate the rapid reversibility of this effect. These two new analogues are promising leads for the development of vascular-disrupting agents in the podophyllotoxin series.

The first N1-alkyl-4-amino-1,2-dihydroquinoline-lactone has been prepared by a five-step sequence in a 51% overall yield via the corresponding furo[3,4-b]quinolin-1(3H)-one. A new practical synthesis of this intermediate was carried out using versatile, commercially available starting materials and constitutes the shortest and highest yielding route. These synthetic pathways could be widened with a view toward the preparation of different substituted derivatives, which could be considered as rigid aminologues of 4-aza-2,3-didehydropodophyllotoxins.

Podophyllotoxin, a natural lignan, is a good inhibitor of tubulin polymerization with antitumoral properties but it is too toxic for therapeutic use. In order to obtain less toxic drugs, several heterolignans have been prepared. We presented the synthesis and preliminary pharmacological properties of 4-aza-2,3-didehydropodophyllotoxins (dihydropyrrole [3,4-b]quinolin-1-ones), a new azalignan series. A straightforward synthesis was described according to a multicomponent reaction in a one-pot procedure. Starting from an aniline, an aromatic aldehyde, and a cyclic B-diketone, many substituted analogues could be prepared. Our lead, the 4-aza-2,3-didehydropodophyllotoxin, is extremely cytotoxic on various tumor cell lines, active in vivo on murine tumors. Like podophyllotoxin, this drug inhibits microtubule assembly without any effect on depolymerization.

[reaction: see text] A convergent method has been found to prepare 4-aza-2,3-didehydropodophyllotoxin and derivatives in a one-pot procedure. The mechanism of the reaction between tetronic acid, anilines, and benzaldehydes is discussed.

Tubulin being a major cellular target for antitumor drugs, tubulin-interacting compounds have attracted great attention as antimitotic agents. Two main classes of antimitotic drugs are known and one of them includes podophyllotoxin, a natural product. The clinical use of podophyllotoxin in the treatment of cancer has been limited by severe toxic side effects. In an attempt to find less toxic analogues, many podophyllotoxin derivatives have been prepared. Identification of two types of mechanisms of action has led to the development of two groups of podophyllotoxin analogues: tubulin polymerisation inhibitors and topoisomerase II inhibitors. The present article focuses on the first group of podophyllotoxin analogues i.e. those that retain "podophyllotoxin-like" activity. The review starts with a short summary of the structural characteristics of tubulin and its interactions with drugs that affect the microtubule dynamics and then deals with the particular case of podophyllotoxin. Particular attention is given to the nature and the location of the binding sites compared to those of colchicine. The main purpose of the present review being the search for structure-activity relationships, the structural significant features required for antitubulin activity are described and discussed in details.