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Query: UMLS:C0338671 (Steroids)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Various classes of inhibitor of 2,3-oxido squalene cyclase have been synthesized and tested on rat liver and Saccharomyces cerevisiae microsomes, 3T3 fibroblast cultures, and various bacteria, fungi, and yeasts. The compounds include azasqualenes, azasqualanes, bis-azasqualenes, bis-azasqualanes, and N-oxide and ammonium derivatives of squalene. In order to better mimic the transition state involved in the SN2-like opening of 2,3-oxidosqualene, we synthesized squalene N-methyloxaziridine. Other derivatives tested were N-methylimine, aminalic hydroperoxide, and N-methylamide. We also attempted to produce new "suicide" inhibitors of SO cyclase, such as a squalenoid epoxide vinyl ether. Many of the products described inhibited the various cyclases, the best having an IC50 of 0.3 microM on plants and 1.5 microM on rat liver microsomes, and good antibacterial and antifungal activity. In a search for inhibitors of squalene epoxidase, a series of mono- and bifunctional squalenoid acetylenes and allenes were synthesized. Some of them proved to be inhibitors of squalene epoxidase.
Steroids
PMID:Drug design based on biosynthetic studies: synthesis, biological activity, and kinetics of new inhibitors of 2,3-oxidosqualene cyclase and squalene epoxidase. 267 8

Epimerizations of 16 alpha-chloro- (1a), bromo- (1b), and iodo-3 beta-hydroxy-5-androsten-17-one (1c) by a brief treatment with 0.2 equiv NaOH in aqueous pyridine reached equilibrium between 16 alpha- and 16 beta-halo ketones. 16 alpha-/16 beta-Halo ketone ratios at equilibrium were 1.5 for Cl, 1.25 for Br, and 1.0 for I. Kinetic analysis showed that compounds 1a-c were stereoselectively converted to the corresponding 16 alpha-hydroxy derivative 3 by an SN2 mechanism, in which the order of the apparent reactivity was Br greater than I greater than Cl. The hydrolysis of a number of 16 alpha-bromo-17-ketones and 2 alpha-bromo-3-ketones was carried out. The yields of the corresponding alcohols were found to depend on remote structural features in the steroids.
Steroids 1985 May
PMID:Stereoselective hydrolysis of 16 alpha-halo-17-keto steroids and long-range substitution effects on the hydrolysis of 16 alpha-bromo-17-ketones and 2 alpha-bromo-3-ketones. 383 59

A mechanistic study on the nucleophilic substitution of a strictly geometric 21-bromo-3alpha-hydroxyl-3beta-methoxymethyl-5alpha-pregnan-20-one was described. Reaction of the alpha-bromoketone with excess lithium imidazole followed by the addition of extra bases including n-butyllithium, methyllithium, lithium piperidine, and lithium pyrrolidine provided unexpected alpha-nucleophilic carbonyl adducts that derived from strong base. Data from HPLC and proton NMR suggested an epoxide as the intermediate. Two possible reaction pathways were proposed for the nucleophilic substitution reaction. One pathway is the normal SN2 substitution reaction, directly provided the imidazoly product without the formation of the unexpected alpha-substituted products. The other pathway went through an epoxide intermediate, in which imidazole anion or the strong bases added would attack from the less hindered site of the epoxide to give the substitution product.
Steroids 2006 Nov
PMID:The mechanism investigation in substitution of 21-bromo-3alpha-hydroxyl-3beta-methoxymethyl-5alpha-pregnan-20-one with nucleophiles. 1693 20

Steroids from Solanum nudum (SNs) have demonstrated antiplasmodial activity against erythrocytic stages of the Plasmodium falciparum strain FCB-2. It is well known that steroids can alter the membrane function of erythrocytes. Thus, we assessed alterations in the membranes of uninfected red blood cells, the parasite invasiveness and the solute-induced lysis of parasitised red blood cells (pRBCs). induced by SNs. We found that most merozoites were unable to invade SN-treated erythrocytes. However, transmission electron microscopy revealed no effect on the morphology of uninfected erythrocytes treated with either SN2 or diosgenone and neither SN induced haemolysis of uninfected erythrocytes. SN2 and SN4 inhibited isosmotic sorbitol and alanine-induced haemolysis of pRBCs. In contrast, diosgenone and SN1 did not inhibit solute-induced haemolysis. The inhibition of solute-induced lysis of parasitised erythrocytes by SN2 and SN4 suggest an action of these SNs on new permeability pathways of pRBCs.
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PMID:Effect of Solanum nudum steroids on uninfected and Plasmodium falciparum-infected erythrocytes. 1982 Aug 25