title: Chemical synthesis and biological evaluation of cis- and trans-12,13-cyclopropyl and 12,13-cyclobutyl epothilones and related pyridine side chain analogues.
abstract: The design, chemical synthesis, and biological evaluation of a series of cyclopropyl and cyclobutyl epothilone analogues (3-12, Figure 1) are described. The synthetic strategies toward these epothilones involved a Nozaki-Hiyama-Kishi coupling to form the C15-C16 carbon-carbon bond, an aldol reaction to construct the C6-C7 carbon-carbon bond, and a Yamaguchi macrolactonization to complete the required skeletal framework. Biological studies with the synthesized compounds led to the identification of epothilone analogues 3, 4, 7, 8, 9, and 11 as potent tubulin polymerization promoters and cytotoxic agents with (12R,13S,15S)-cyclopropyl 5-methylpyridine epothilone A (11) as the most powerful compound whose potencies (e.g. IC(50) = 0.6 nM against the 1A9 ovarian carcinoma cell line) approach those of epothilone B. These investigations led to a number of important structure-activity relationships, including the conclusion that neither the epoxide nor the stereochemistry at C12 are essential, while the stereochemistry at both C13 and C15 are crucial for biological activity. These studies also confirmed the importance of both the cyclopropyl and 5-methylpyridine moieties in conferring potent and potentially clinically useful biological properties to the epothilone scaffold.
authors.affiliation: Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Nicolaou
authors.forename: K
authors.initials: K
authors.lastname: Namoto
authors.forename: A
authors.initials: A
authors.lastname: Ritzén
authors.forename: T
authors.initials: T
authors.lastname: Ulven
authors.forename: M
authors.initials: M
authors.lastname: Shoji
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: G
authors.initials: G
authors.lastname: D'Amico
authors.forename: D
authors.initials: D
authors.lastname: Liotta
authors.forename: C T
authors.initials: CT
authors.lastname: French
authors.forename: M
authors.initials: M
authors.lastname: Wartmann
authors.forename: K H
authors.initials: KH
authors.lastname: Altmann
authors.forename: P
authors.initials: P
authors.lastname: Giannakakou
mesh_terms: D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy; D004354:Drug Screening Assays, Antitumor; D004852:Epoxy Compounds / Q000138:chemical synthesis* / Q000494:pharmacology*; D005260:Female; D006801:Humans; D010051:Ovarian Neoplasms / Q000188:drug therapy; D011725:Pyridines / Q000138:chemical synthesis* / Q000494:pharmacology*; D013844:Thiazoles / Q000138:chemical synthesis* / Q000494:pharmacology*; D014404:Tubulin / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D004852:Epoxy Compounds; D011725:Pyridines; D013844:Thiazoles; D014404:Tubulin