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At least 1,387 records · Page 77Linked to original sources
PubMed2005

Configuration of the psymberin amide side chain.

[structure: see text] The structure of the amide side chain of psymberin, a potent and selective cytotoxin, is proposed. Syn and anti models of the amide side chain were prepared, and the structural assignment was confirmed by X-ray crystallographic analysis of the anti isomer. Comparison of (1)H and (13)C NMR data establishes homology between the natural product and the synthetic model compound of anti configuration and not the corresponding syn isomer.

Amides↗
PubMed2005

Apoptolidins B and C: isolation, structure determination, and biological activity.

[reaction: see text] Apoptolidin (1) is a promising new therapeutic lead that exhibits remarkable selectivity against cancer cells relative to normal cells. We report the isolation, characterization, solution structure, stability, and biological activity of two new members of this family: apoptolidins B (2) and C (3). These new agents are found to have antiproliferative activity on par with or better than apoptolidin itself in an assay with H292 lung cancer cells.

Actinobacteria↗
PubMed2005

Stereochemical assignment of the C1-C6 fragment of psymberin by synthesis and natural product degradation.

[reaction: see text] Psymberin is a sponge-derived natural product that shows striking selectivity as a cytotoxic agent. Conformational mobility has precluded stereochemical assignment for the acyl fragment of this molecule (psymberic acid) by NMR. Herein we report stereoselective syntheses of all four stereoisomers of psymberic acid. A comparison of the acid-mediated cyclization products of these compounds to the product of psymberin's acidic methanolysis showed the stereochemical configuration of this fragment to be 4S,5S.

Amides↗
PubMed2005

Functionally layered dendrimers: a new building block and its application to the synthesis of multichromophoric light-harvesting systems.

[reaction: see text] A divergent synthesis of internally functionalized dendrimers based on a modular functional monomer has been developed. This strategy was applied to the construction of a light-harvesting dendrimer containing one set of naphthopyranone dyes located at the interior and another set of coumarin chromophores located in the adjacent outer layer surrounding a porphyrin acceptor. Quantitative energy transfer from both donor pigments is observed, giving rise to exclusive emission from the porphyrin core over all excitation wavelengths.

Dendrimers↗
PubMed2005

Design, total synthesis, and evaluation of C13-C14 cyclopropane analogues of (+)-discodermolide.

[structure: see text] The design, total synthesis, and biological evaluation of two C13-C14-cyclopropyl analogues [(+)-1 and (+)-2] of (+)-discodermolide have been achieved. Key features of the syntheses include highly stereoselective, hydroxyl-directed cyclopropanations of vinyl iodides and higher order cuprate-mediated cross-coupling reactions between cyclopropyl iodides and alkyl iodides. Biological evaluation revealed that neither orientation of the cyclopropyl methylene completely substitutes for the C14 methyl found in (+)-discodermolide (3).

Alkanes↗
PubMed2005

Total synthesis of (-)-SNF4435 C and (+)-SNF4435 D.

[reaction: see text] A convergent, biomimetic total synthesis of the immunosuppressant polyketides SNF4435 C and D is described. The synthetic pathway features a stereo- and regioselective [3,3]-sigmatropic rearrangement as well as a high-yielding Stille coupling/8pi-6pi electrocyclization cascade.

Crystallography, X-Ray↗
PubMed2005

Photosensitized conversion of 9,10-deoxytridachione to photodeoxytridachione.

[reaction: see text] The photochemical conversion of 9,10-deoxytridachione to photodeoxytridachione has been photosensitized. The conversion was also quenched by piperylene. Photodeoxytridachione was produced in good yields under conditions in which only the cyclohexadiene group is sensitized. The results show that some, and perhaps all, of the photoreactions of 9,10-deoxytridachione occur through a triplet excited state. The mechanistic and biosynthetic implications of these results are discussed.

Alkadienes↗
PubMed2005

Concise and stereoselective synthesis of the N7-C25 fragment of psymberin.

[reaction: see text] The N7-C25 fragment of the potent and selective cytotoxic agent psymberin has been prepared through a short (12 linear steps, 15 total steps) and stereoselective sequence. Highlights of this route include a very rapid construction of the pentasubstituted arene, a substrate-controlled diastereoselective fragment coupling using a Mukaiyama aldol reaction, and an efficient entry into a key tetrahydropyranyl cyanide.

Catalysis↗
PubMed2005

Design, synthesis, and biological evaluation of simplified analogues of (+)-discodermolide. Additional insights on the importance of the diene, the C7 hydroxyl, and the lactone.

[structure: see text] The design, synthesis, and biological evaluation of seven totally synthetic analogues of the antitumor agent (+)-discodermolide are reported. Saturation of the terminal diene system, alteration of the substituents on the lactone, and alkylation of the C7-hydroxyl group reveal significant structure-activity relationships.

Alkanes↗
PubMed2005

Phelligridimer A, a highly oxygenated and unsaturated 26-membered macrocyclic metabolite with antioxidant activity from the fungus Phellinus igniarius.

[structure: see text] A highly oxygenated and unsaturated 26-membered macrocyclic metabolite, phelligridimer A (1), has been isolated from the Chinese medicinal fungus Phellinus igniarius. Its structure was elucidated by spectroscopic methods. A possible biogenesis of 1 mediated by the fungal metabolite hispidin was postulated. Phelligridimer A showed antioxidant activity (IC50 of 10.2 microM) but was inactive to several human cancer cell lines (IC50 > 50 microM) and enzymes PTP1B (IC50 > 25 microM) and thrombin (IC50 > 10 microM).

Animals↗
PubMed2005

A total synthesis of tarchonanthuslactone exploiting N-pyrrole carbinols as efficient stereocontrolling elements.

[reaction: see text] A short stereoselective total synthesis of the polyketide natural product, tarchonanthuslactone, has been achieved. The key sequence involves the first reported catalytic enantioselective reduction of an N-acyl pyrrole and subsequent use of this stereocenter in a diastereoselective reductive cascade. This proceeded with unprecedentedly high stereocontrol and offered an elegant method of generating the desired syn stereochemistry present in the final target in one step.

Biological Products↗
PubMed2006

Polyenylpyrroles and polyenylfurans from an Australian Isolate of the soil ascomycete Gymnoascus reessii.

[structure: see text] An Australian isolate of the soil ascomycete Gymnoascus reessii yielded a series of cytotoxic metabolites, including the known polyenylpyrroles rumbrin (1) and auxarconjugatin A (2), and the new rumbrin stereoisomer 12E-isorumbrin (3), as well as an unprecedented class of polyenylfurans exemplified by gymnoconjugatins A (4) and B (5). Structures were assigned with detailed spectroscopic analysis.

Antineoplastic Agents↗
PubMed2006

Synthesis of pterocellin A.

The first total synthesis of pterocellin A (1) was achieved in 10 linear steps from commercially available kojic acid (6) and 2-bromo-3-pyridinol (11) in a convergent sequence. The key constructive steps are a directed lithiation to couple two pyridines and an intramolecular nucleophilic aromatic substitution to form 1. [structure: see text]

Alkaloids↗
PubMed2006

Total synthesis of topopyrones B and D.

[reaction: see text] We describe a straightforward synthesis of topopyrones B and D, which are potent and selective inhibitors of topoisomerase I. The chemistry should be suitable for additional structure-activity relationship (SAR) work.

Anthraquinones↗
PubMed2006

A rapid divergent synthesis of highly substituted delta-lactones.

[reaction: see text] Nucleophilic 1,2-addition of (Z)-gamma-silyloxyvinylzinc reagents to ethyl glyoxylate followed by desilylation and cyclization affords 3,6-dihydro-3-hydroxypyran-2-ones in good chemical yields. In situ formation of allylic phosphates followed by reaction with RCu(CN)Li reagents affords substituted 5,6-dihydropyran-2-ones. The parent compound, 3,6-dihydro-3-hydroxypyran-2-one, undergoes allylic phosphate formation, cuprate-mediated allylic substitution, and 1,4-conjugate addition to afford trans-4,5-disubstituted tetrahydropyran-2-ones in a one-pot process.

Catalysis↗