The synthesis of the monomeric moiety of disorazole C1

Syntheses of Cyclopropyl Analogues of Disorazoles A1 and B1 and Their Thiazole Counterparts

Modular syntheses of disorazoles A₁ and B₁ analogues in which the epoxide moieties of the natural products were replaced with cyclopropyl units have been achieved. Targeted as part of a structure-activity relationships study, these syntheses were successfully extended to the thiazole counterparts of these analogues. The retrosynthetically defined fragments were assembled through Yamaguchi esterification, Cu/Pd-catalyzed cross-coupling, Yamaguchi macrolactonization, and Cu-catalyzed cross-coupling as the key reactions. Further synthetic and biological investigations of such analogues are expected to lead to the discovery and development of potential payloads for antibody-drug conjugates as targeted cancer therapies.

Isolation, biology and chemistry of the disorazoles: new anti-cancer macrodiolides

Covering: 1994 to 2008. The disorazoles comprise a family of 29 closely related macrocyclic polyketides isolated in 1994 from the fermentation broth of the gliding myxobacterium Sorangium cellulosum. Disorazoles A1, E and C1 have shown exceptional biological activites toward inhibiting the proliferation of human cancer cell lines in picomolar and nanomolar concentrations through the disruption of microtubule polymerization. This review gives a brief introduction describing the biosynthesis and the significance of the disorazoles as a new class of microtubulin disruptors. Another portion of the review focuses on the biology of the disorazoles, specifically disorazole A1 and C1, and their antiproliferative efficacy against animal and human tumor cell lines, as well as the available SAR data. The majority of the discussion addresses synthetic efforts, including partial syntheses of various disorazoles and a summary of the total synthesis of disorazole C1.

From natural products to biological tools

The development of a total synthetic approach for the antimitotic disorazole C1 and the design of a peptide isostere linked to the reactive oxygen scavenger 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) demonstrate established as well as novel strategies for mining the therapeutic potential of natural products.

Cellular analysis of disorazole C and structure-activity relationship of analogs of the natural product

Structure-activity analyses of synthetic disorazole C(1) and eight of its analogs indicate that the presence of a vinyl oxirane moiety or a tetraene sequence is not necessary for potent cytotoxic and antimitotic properties. Using an automated multiparameter fluorescence-based cellular assay to simultaneously probe the effects of disorazole analogs on cellular microtubules, mitotic arrest, and cytotoxicity, we found that disorazole C(1) enhanced the mitotic index and chromatin condensation and arrested cells in the G2/M phase of the cell cycle. All structural analogs and synthesis precursors of disorazole C(1) were at least two orders of magnitude less potent than the parent compound, thus indicating that both the functional group array and the three-dimensional conformation of the parent compound are critical for interaction with the biological target. We conclude that disorazole C(1) is a potent inducer of mitotic arrest and hypothesize that this biological activity may be mediated by microtubule perturbation.

Methanolysis products of disorazole A1

Two new disorazole analogues were synthesized by acid-promoted methanolysis of disorazole A1 (1). Structural elucidation of both products (2 and 3), through 1D and 2D NMR experiments, verified that each resulted from epoxide cleavage. With antiproliferative activities in susceptible cell lines comparable to that of disorazole A1, these methanolysis products indicate that the C-9-C-10 epoxide is not an essential structural component for biological activity.

Toward the total synthesis of disorazole A(1) and C(1): asymmetric synthesis of a masked southern segment

[reaction: see text] A highly convergent asymmetric synthesis of the masked southern segment of the antimitotic agent disorazole A(1) involves a Sonogashira coupling between a C1'-C10' enyne and a suitably protected C11'-C19' vinyl iodide. The central E,Z,Z-triene moiety is masked as a more stable ynediene.

Studies on the total synthesis of disorazole C1. An advanced macrocycle intermediate

Synthesis of protected tetradehydro-(6,6'-S)-(14,14'-S)-(16,16'-R)-disorazole (3), a potential precursor to the natural product disorazole C1 (1), is described. Key features of this work include (a) an unprecedented sequential 1,5 O --> O silyl rearrangement/Horner-Wadsworth-Emmons reaction used to construct 18, (b) a highly convergent Sonogashira reaction between the dienyl iodide 7 and the alkyne 8 to assemble the dienyne monomeric fragment 5, and (c) the selective cyclization of 5 to give either the cyclic monomer 23 or the dimer 3.