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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)
The asymmetric (er > 99:1) total synthesis of (+)-anti- and (-)-syn-mefloquine hydrochloride from a common intermediate is described. The Sharpless asymmetric dihydroxylation is the key asymmetric tra...
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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...
Vitamin D(Vit D) is a pro-differentiation agent that enhances the accumulation of protoporphyrin IX (PpIX) after MAL(methyl-aminolevulinate) incubation in actinic keratosis and may have si...
This study will help define the best tolerated approach to cystoscopy by randomly comparing the flexible to the rigid cystoscope.
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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)