A flexible asymmetric approach to methyl 5-alkyltetramates and its application in the synthesis of cytotoxic marine natural product belamide a.
Summary of "A flexible asymmetric approach to methyl 5-alkyltetramates and its application in the synthesis of cytotoxic marine natural product belamide a."
By using a methyl tetramate derivative (R)- or (S)-9 as a novel chiral building block, a direct, flexible, and highly enantioselective approach to methyl (R)- or (S)-5-alkyltetramates (2) is disclosed. Among the synthesized methyl 5-alkyltetramates 2, methyl 5-methyltetramate (2 a) is found in cytotoxic mirabimide E (4) and dysideapyrrolidone (5), and methyl 5-benzyltetramate (2 g) is a substructure in the potent antineoplastic dolastatin 15 (3). On the basis of this method, the first asymmetric synthesis of the antimitotic tetrapeptide belamide A (7) has been achieved in seven steps from (S)-9, with an overall yield of 23.8 %. Not only have the structure and absolute configuration of (+)-belamide A (7) been confirmed, but also the solvent used for recording the (13) C NMR spectrum, the (13) C NMR spectrum data correlation, and optical rotation data of natural belamide A (7) have been revised.
This article was published in the following journal.
Name: Chemistry (Weinheim an der Bergstrasse, Germany)
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/21226113
- DOI: http://dx.doi.org/10.1002/chem.201002063
In 1989, the asymmetric Mukaiyama aldol reaction mediated by a Lewis acid consisting of a chiral diamine and Sn(II) triflate was reported. The asymmetric Mukaiyama aldol reaction is now widely used as...
The first asymmetric organocatalytic synthesis of helicenes is reported. A novel SPINOL-derived phosphoric acid, bearing extended π-substituents, catalyzes the asymmetric synthesis of helicenes throu...
A simple and highly efficient approach to hydroxylated pyrrolizidine and indolizidine is developed from an aldehyde as a starting material using organocatalytic and asymmetric dihydroxylation reaction...
A novel catalytic enantioselective synthesis of functionalized 1,3-enynes has been developed featuring the design and synthesis of conjugated nitro dienynes as a useful new class of Michael acceptors....
A flexible total synthesis of the 2-nitropyrrole-derived marine natural product, (+)-heronapyrrole C, is reported. The approach is based on regioselective access to key building blocks containing the ...
The study will help define the best tolerated approach to cystoscopy in women by randomly comparing flexible to rigid cystoscopy. Previous randomized studies evaluated rigid cystoscopy und...
This study will help define the best tolerated approach to cystoscopy by randomly comparing the flexible to the rigid cystoscope.
The purpose of this work is to estimate the efficiency in terms of pain of the application of a local anesthetic (xylocaïne viscous 2%®) during the realization of an examination in naso-...
Cholesterol is the precursor of glucocorticoids, mineralocorticoids and sex steroids. Both adrenal and non-adrenal (ovarian + testicular) all steroid hormones are primarily synthesized usi...
The study is in two parts Part one of the study describes the use of the new single-use flexible video-scope for intubation of patients with predicted normal airways. Part two comp...
Medical and Biotech [MESH] Definitions
A cytotoxic polypeptide quinoxaline antibiotic isolated from Streptomyces echinatus that binds to DNA and inhibits RNA synthesis.
(1 beta,2 alpha,11 beta,12 alpha,15 beta(S))-11,20-Epoxy-1,2,11,12-tetrahydroxy-15-(2-hydroxy-2-methyl-1-oxobutoxy)picras-3-en-16-one. A quassinoid (Simaroubolide) from Simaruba glauca, a tropical shrub. It has been used as an antiamebic agent and is found to be cytotoxic. It may be of use in cancer chemotherapy.
Any situation where an animal or human is trained to respond differentially to two stimuli (e.g., approach and avoidance) under reward and punishment conditions and subsequently trained under reversed reward values (i.e., the approach which was previously rewarded is punished and vice versa).
A cytokine which resembles IL-1 structurally and IL-12 functionally. It enhances the cytotoxic activity of NK CELLS and CYTOTOXIC T-LYMPHOCYTES, and appears to play a role both as neuroimmunomodulator and in the induction of mucosal immunity.
Brief therapeutic approach which is ameliorative rather than curative of acute psychiatric emergencies. Used in contexts such as emergency rooms of psychiatric or general hospitals, or in the home or place of crisis occurrence, this treatment approach focuses on interpersonal and intrapsychic factors and environmental modification. (APA Thesaurus of Psychological Index Terms, 7th ed)