RESUMEN

D-Ring-seco-limonoids (tetranortriterpenoids), such as gedunin and xylogranin B display anti-cancer activity, acting via inhibition of Hsp90 and/or associated chaperon machinery (e.g., p23). Despite this, these natural products have received relatively little attention, both in terms of an enabling synthetic approach (which would allow access to derivatives), and as a consequence their structure-activity relationship (SAR). Disclosed herein is a generally applicable synthetic route to the BCD ring system of the seco-D-ring double bond containing limonoids. Furthermore, cell based assays revealed the first skeletal fragment that exhibited inhibition of the p23 enzyme at a level which was equipotent to that of gedunin, despite being much less structurally complex.

RESUMEN

The first seco-casbane, EBC-329, isolated from the Australian rainforest, was synthesised from (+)-2-carene in seven steps. This endeavour not only established the absolute stereochemical assignment as (8R,9S)-EBC-329, but also identified, via photoisomerisation, a new seco-casbane family member.

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RESUMEN

Gedunin, first isolated in 1960, displays a remarkable range of biological activity, but has yet to receive dedicated synthetic attention from a ground up construction perspective. Presented herein is a successfully executed approach to the fully functionalized ABC ring system of this challengingly complex natural product.

RESUMEN

A titanocene-catalyzed multicomponent coupling is described herein. Using catalytic titanocene, phosphine, and zinc dust, zinc acetylides can be generated from the corresponding iodoalkynes to affect sequential nucleophilic additions to aromatic aldehydes. The intermediate propargylic alkoxides are trapped in situ with acetic anhydride, which are susceptible to a second nucleophilic displacement upon treatment with a variety of electron-rich species, including acetylides, allyl silanes, electron-rich aromatics, silyl enol ethers, and silyl ketene acetals. Additionally, employing cyclopropane carboxaldehydes led to ring-opened products resulting from iodine incorporation. Taken together, these results form the basis for a new mode of three-component coupling reactions, which allows for rapid access to value added products in a single synthetic operation.

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RESUMEN

The titanocene-catalyzed construction of all-carbon substituted tertiary centers directly from aromatic aldehydes is described. The starting aldehyde behaves as a traceless functionality in the formation of multiple carbon-carbon bonds through consecutive carbon-heteroatom bond activations. The sequential addition of a metal acetylide and a second carbon nucleophile to the dielectrophilic aldehyde enables the construction of symmetrical and unsymmetrical 1,4-diynes in good yields.

RESUMEN

In the first comprehensive biological assessment of the tambjamine class of marine alkaloids, synthetically derived samples of compounds 1-9 have been subjected to evaluation as antimicrobial agents and screened for their cytotoxic effects on various human cancer cell lines. Most were strongly active against the fungus Malassezia furfur (>amphotericin B) and showed considerable, but non-selective, antiproliferative activity against both human cancer and normal cell lines. Tambjamines I and J (6 and 7, resp.) displayed significant apoptosis-inducing effects.

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RESUMEN

A SAMPLE OF THE TITLE COMPOUND [SYSTEMATIC NAME: (1aS,2aS,3S,5aS,6aS,7R,7aS,7bS,8R,8aS,10R)-7-hydr-oxy-3-(1-meth-oxy-1-methyl-ethyl)-10-(2-methyl-1-propen-yl)-1a,5a,6a,7,7a,7b,8,8a-octa-hydro-2H-8,2a-(epoxy-methano)phenanthro[2,3-b:6,7-b']bis-oxirene-2,5(3H)-dione], C(23)H(28)O(7), was generated by enanti-oselective synthesis. There are three mol-ecules of the compound in the crystallographic asymmetric unit. Hydrogen bonding between alcohol H atoms and keto groups of adjacent mol-ecules appears to stabilize the structure. The compound is enanti-omerically pure but the absolute configuration could not be determined directly in this study. Accordingly, the illustrated configuration was assigned on the basis of the nature of the chiral nonracemic precursor used in the synthesis.

RESUMEN

The enantiomerically pure and readily available metabolites 10-12 have been converted over four simple steps into the epoxyquinol derivatives 22-24, respectively. Compounds 23 and 24 or their immediate precursors have been exploited in efficient total syntheses of (-)-bromoxone (ent-1), (-)-epiepoformin (ent-2), (-)-harveynone (4), (+)-panepophenanthrin (6), and (+)-hexacyclinol (9).

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RESUMEN

The acetate salts of tambjamines C, E, and F (2-4, respectively), as well as those of the related alkaloids BE-18591 (5) and 6, have been prepared by treatment of bipyrrole aldehyde 16 with the relevant amine in the presence of acetic acid. The 5'-bromo-analogue, 30, of compound 16 has also been prepared and used to obtain the acetate salts of tambjamines G, H, I, and J (8-11 respectively).

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