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Results for “macrocycles”

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At least 919 records · Page 51Linked to original sources
PubMed2001

Synthesis and biological evaluation of novel macrocyclic paclitaxel analogues.

[reaction: see text] This work describes the synthesis of two novel macrocyclic taxoid constructs by ring-closing olefin metathesis (RCM) and their biological evaluation. Computational studies examine conformational profiles of 1 and 2 for their fit to the beta-tubulin binding site determined by electron crystallography. The results support the hypothesis that paclitaxel binds to microtubules in a "T" conformation.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Efficient assembly of the phomactin core via two different macrocyclization protocols.

[reaction--see text] The core structure of phomactins C and D was assembled by an efficient strategy starting from 3,4-dimethylcyclohexen-2-one. Key reactions include (1) a high yielding and highly diastereoselective Michael addition of a mixed cuprate, (2) a carbonylative alkyne-enoltriflate coupling or an intramolecular addition of an acetylide onto an aldehyde to form the macrocycle, (3) chemoselective Michael addition of a cuprate to an enynone, to give the carbon framework of desformyl phomactin C or D, and finally (4) regioselective addition of a thia-nucleophile to the more reactive beta-position of the resulting dienone.

Crystallography, X-Ray↗
PubMed2003

Efficient synthesis of macrocyclic paracyclophanes by ring-closing metathesis dimerization and trimerization reactions.

Ring-closing metathesis reactions of para-disubstituted aromatic substrates produced macrocyclic [n.n]-, and [n.n.n]paracyclophanes efficiently through dimerization and trimerization reactions. Sufficiently long alkyl chains allowed direct monocyclizations to yield [n]paracyclophanes. A small library of paracyclophanes were generated by the combinatorial cross-metathesis approach.

Journal Article↗
PubMed2003

Synthesis of muscothiazoles A and B: Critical role of methyl group substitution in RCM-based syntheses of macrocycles.

[reaction: see text] Muscothiazoles A (2b) and B (2c) have been prepared by two approaches that differ in the order of assembly of the rings. Comparative studies show that substitution of the carbon chains in substrate 5 or 12 (respective precursors to 13-membered and 14-membered rings by RCM), even by a single methyl group, can have a profound effect on increasing the efficiency of the macrocyclization.

Journal Article↗
PubMed2003

Difficult macrocyclizations: new strategies for synthesizing highly strained cyclic tetrapeptides.

[reaction: see text] Cyclic tetrapeptides are an intriguing class of natural products. To synthesize highly strained cyclic tetrapeptides we developed a macrocyclization strategy that involves the inclusion of 2-hydroxy-6-nitrobenzyl (HnB) group at the N-terminus and in the "middle" of the sequence. The N-terminal auxiliary performs a ring closure/ring contraction role, and the backbone auxiliary promotes cis amide bonds to facilitate the otherwise difficult ring contraction. Following this route, the all-L cyclic tetrapeptide cyclo-[Tyr-Arg-Phe-Ala] was successfully prepared.

Amides↗
PubMed2003

New oxazole-based peptidomimetics: useful building blocks for the synthesis of orthogonally protected macrocyclic scaffolds.

[structure: see text] The synthesis of a new family of densely functionalized oxazole-containing amino acids is described. These building blocks were employed for preparing macrocycles containing Lys and Glu residues by a combination of solid- and solution-phase synthesis. The resulting structures are presented as orthogonally protected scaffolds for supramolecular chemistry.

Biomimetic Materials↗
PubMed2004

Versatile formation of [2]catenane and [2]pseudorotaxane structures; threading and noncovalent stoppering by a self-assembled macrocycle.

A self-assembled dimeric macrocycle between 4,4'-bis(4-pyridylmethoxy)biphenyl (L) and (en)Pd(NO(3))(2) was constructed, and its interactions with cyclodextrins of different cavity size resulted in the formation of [2]catenane and [2]pseudorotaxane systems, respectively. The structures were identified by 1D and 2D NMR spectroscopy and cold spray ionization mass (CSI-MS) spectrometry.

Journal Article↗
PubMed2004

Metathesis of structurally preorganized bivalent carbohydrates. Synthesis of macrocyclic and oligomeric scaffolds.

[reaction: see text] Bivalent carbohydrate substrates for metathesis were synthesized from glucuronic acid and phenylene-1,4-diamine. The substrate secondary structure depends on whether secondary or tertiary amides are present, and this influences the course of the metathesis reaction leading to novel multivalent scaffolding. Molecular modeling suggests that a very rigid macrocyclic scaffold has potential for the development of alpha-helix peptidomimetics.

Carbohydrates↗
PubMed2004

Three-carbon ring expansion by cyclopropane insertion: macrocyclic musks from readily available C-12 starting materials.

A thermal three-carbon ring expansion based on side chain ring insertion of a cyclopropane moiety is described. Flash vacuum pyrolysis (FVP) of 1-cyclopropyl-cycloalk-3-enol derivatives leads to the three-carbon ring expanded enones with clean retention of double bond geometry. Substrates bearing methyl groups on the cyclopropane ring undergo regioselective bond cleavage, allowing for the systematic preparation of selectively substituted macrocyclic musks from low-priced C-12 starting compounds.

Journal Article↗
PubMed2004

Strained aromatic oligoamide macrocycles as new molecular clips.

Can one join both ends of a helix? A helical aromatic oligoamide was macrocyclized into a saddle-shaped bifunctional clip molecule that self-assembles into discrete circular dodecamers in the solid state and shows great potential for binding aromatic acid guests in solution. The cyclization step requires that the helix is only partly denatured in the reaction medium.

Journal Article↗