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PubMed2006

Discovery of thiochroman and chroman derivatives as pure antiestrogens and their structure-activity relationship.

In order to develop pure antiestrogens, a series of 7-hydroxy-3-(4-hydroxyphenyl)-3-methylchroman and 7-hydroxy-3-(4-hydroxyphenyl)-3-methylthiochroman derivatives with sulfoxide containing side chains at the 4-position were designed, synthesized, and evaluated. Among them, compounds 14b and 24b functioned as pure antiestrogens with the ability to downregulate ER, and their in vitro and in vivo antiestrogen activities were similar to those of ICI182,780. In addition, the structure-activity relationship indicated that the (3RS,4RS)-configuration between the 3- and 4-position, the methyl group at the 3-position, the 9-methylene chain between the scaffold and the sulfoxide moiety, and the terminal perfluoroalkyl moiety play an important role in increasing estrogen receptor binding and oral antiestrogen activities.

Animals↗
PubMed2003

Direct evidence for recycling of myeloperoxidase-catalyzed phenoxyl radicals of a vitamin E homologue, 2,2,5,7,8-pentamethyl-6-hydroxy chromane, by ascorbate/dihydrolipoate in living HL-60 cells.

Myeloperoxidase (MPO)-catalyzed one-electron oxidation of endogenous phenolic constituents (e.g., antioxidants, hydroxylated metabolites) and exogenous compounds (e.g., drugs, environmental chemicals) generates free radical intermediates: phenoxyl radicals. Reduction of these intermediates by endogenous reductants, i.e. recycling, may enhance their antioxidant potential and/or prevent their potential cytotoxic and genotoxic effects. The goal of this work was to determine whether generation and recycling of MPO-catalyzed phenoxyl radicals of a vitamin E homologue, 2,2,5,7,8-pentamethyl-6-hydroxychromane (PMC), by physiologically relevant intracellular reductants such as ascorbate/lipoate could be demonstrated in intact MPO-rich human leukemia HL-60 cells. A model system was developed to show that MPO/H(2)O(2)-catalyzed PMC phenoxyl radicals (PMC*) could be recycled by ascorbate or ascorbate/dihydrolipoic acid (DHLA) to regenerate the parent compound. Absorbance measurements demonstrated that ascorbate prevents net oxidation of PMC by recycling the phenoxyl radical back to the parent compound. The presence of DHLA in the reaction mixture containing ascorbate extended the recycling reaction through regeneration of ascorbate. DHLA alone was unable to prevent PMC oxidation. These conclusions were confirmed by direct detection of PMC* and ascorbate radicals formed during the time course of the reactions by EPR spectroscopy. Based on results in the model system, PMC* and ascorbate radicals were identified by EPR spectroscopy in ascorbate-loaded HL-60 cells after addition of H(2)O(2) and the inhibitor of catalase, 3-aminotriazole (3-AT). The time course of PMC* and ascorbate radicals was found to follow the same reaction sequence as during their recycling in the model system. Recycling of PMC by ascorbate was also confirmed by HPLC assays in HL-60 cells. Pre-loading of HL-60 cells with lipoic acid regenerated ascorbate and thus increased the efficiency of ascorbate in recycling PMC*. Lipoic acid had no effect on PMC oxidation in the absence of ascorbate. Thus PMC phenoxyl radical does not directly oxidize thiols but can be recycled by dihydrolipoate in the presence of ascorbate. The role of phenoxyl radical recycling in maintaining antioxidant defense and protecting against cytotoxic and genotoxic phenolics is discussed.

Antioxidants↗
PubMed2003

Unusual effects in the pd-catalyzed asymmetric allylic alkylations: synthesis of chiral chromans.

An examination of earlier reports of poor-to-modest results using Pd-catalyzed asymmetric allylic alkylations (AAA) to effect cyclization to form tetrasubstituted carbons reveals several novel factors that can influence this class of reactions. Thus, carboxylate has a major effect on such cyclizations wherein the ee increases from 14% ee favoring the S with no carboxylate to 84% ee favoring the R enantiomer in the presence of 1 equiv of carboxylate. Changing the double bond geometry from E to Z further increases the ee to 97%. Furthermore, the chiral catalyst that forms the R enantiomer with the E-alkene forms the S enantiomer with the Z alkene. In contrast to trisubstituted alkene substrates, disubstituted ones show a decrease in ee in going from the E to Z alkenes. The role of carboxylate appears to be a ligand to Pd during the catalytic cycle, a previously unsuspected phenomenon since such reactions are generally believed to involve pi-allylpalladium cationic complexes. The dependence upon alkene geometry helps define the nature of the chiral pocket which better accommodates a Z alkene compared to an E alkene. The results are compatible with the enantiodiscriminating step being ionization which occurs by coordination of the palladium to one of the two prochiral faces of the double bond. A synthesis of (+)-clusifoliol, a constituent of a folk medicine for treatment of malignant tumors, which also assigns the absolute configuration, illustrates the utility of the method.

Alkylation↗
PubMed2003

Formal [3 + 3] cycloaddition approach to chromenes and chromanes. Concise total syntheses of (+/-)-rhododaurichromanic acids A and B and methyl (+/-)-daurichromenic ester.

[reaction: see text] Total syntheses of (+/-)-rhododaurichromanic acids A and B and methyl (+/-)-daurichromenic ester are described here. Despite the complex appearances of these compounds, their syntheses are completed in six steps with a 15% overall yield as a mixture by featuring our formal oxa-[3 + 3] cycloaddition methodology.

Chromans↗
PubMed2003

Total synthesis of the highly potent anti-HIV natural product daurichromenic acid along with its two chromane derivatives, rhododaurichromanic acids A and B.

[reaction: see text] The highly potent anti-HIV natural product daurichromenic acid was successfully synthesized in only five steps with 49% overall yield. The key step in the synthetic strategy involves a microwave-assisted tandem condensation and intramolecular S(N)2'-type cyclization to form the 2H-benzopyran core structure.

Anti-HIV Agents↗
PubMed2003

Antifungal chromans inhibiting the mitochondrial respiratory chain of pea seeds and new xanthones from Calophyllum caledonicum.

Two new xanthones, caledonixanthone M 1 and caloxanthone L 2, and one new acid, caledonic acid 6 were isolated from the hexane-soluble extract of the stem bark of Calophyllum caledonicum. In the course of this phytochemical study, seven other known compounds - calothwaitesixanthone, calozeyloxanthone, allanxanthone, isoapetalic acid 3, calolongic acid 4, apetalic acid 5 and isocalolongic acid 7 - were isolated. Their antifungal activity against the growth of the human pathogenic fungus Aspergillus fumigatus was then investigated. The results indicated that the crude extract, calolongic acid 4 and isocalolongic acid 7 exhibited strong inhibitory effects with MIC (80) values of 8, 4, 2 microg/mL, respectively. Besides, calolongic acid 4, its lactone derivative 4a and isocalolongic acid 7 markedly reduced the respiration of pea seed mitochondria.

Antifungal Agents↗
PubMed1981

[Studies on the circulatory side-effects of 2-[3'-diethylaminopropyl-(1')-carbamoyl]-6,7-dimethoxy-1-thiaiso-chroman-1,1-di oxide ("16-252") (author's transl)].

In view of its application to human beings, the authors tested 3-[3'-diethylaminopropyl-(1')-carbamoyl]-6,7-dimethoxy-1-thiasiochroman-1,1-dio xide ("16-252"), which is a potential antidepressant by its basic neuropharmacological activities, for circulatory side-effects on the rat, the cat and the awake carotid-ligated dog and compared them with those of imipramine. "16-252" differs from imipramine in principle. Whereas imipramine exerts above all a sympathiocomimetic circulatory effect (characterized by tachycardia, increased cardiac output and increased arterial pressure), "16-252" induces bradycardia, a decrease in cardiac output and a reactive increase of the total peripheral resistance. The doses of "16-252" required to bring about more marked circulatory side-effects are about 3-fold higher than those of imipramine. Medium doses of "16-252" do not produce the cardiodepressant effects typical of imipramine and they do not potentiate the action of administered noradrenaline typical of tricyclic antidepressants. The results obtained are discussed from the aspects of cardiotoxic properties in case of long-term therapy.

Animals↗
PubMed2001

3',4'-Bis(4-chlorophenyl)spiro[chroman-3,5'(4'H)-isoxazol]-4-one.

The title compound, C(23)H(15)Cl(2)NO(3), crystallizes with two independent molecules in the asymmetric unit. The chromanone moiety consists of a benzene ring fused with a six-membered heterocyclic ring which adopts a sofa conformation. The five-membered spiroisoxazoline ring is in an envelope conformation. The p-chlorophenyl rings bridged by the five-membered ring are nearly perpendicular to each other. The chromanone moiety of one molecule packs into the cavity formed by the p-chlorophenyl rings of a second molecule through the formation of C-H.pi interactions. The structure is stabilized by weak C-H.O, C-H.Cl and C-H.pi interactions.

Journal Article↗