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Query: CAS:75-07-0 (aldehyde)
 25,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

2-Deoxy-D-arabino-[6-13C]hexose (10), to be used to test the stability of 2-deoxy-D-arabino-hexose 6-phosphate in brain tissue, was prepared. 2-Deoxy-D-arabino-hexose was labeled at C-6 because of the large difference in chemical shift between C-6 in the free sugar and C-6 in the 6-phosphate. The synthetic scheme resembled that used for the synthesis of D-[6-13C]glucose that involved the removal of C-6 from D-glucose followed by its replacement with 13C. The protected derivative methyl 2-deoxy-alpha-D-arabino-hexofuranoside was prepared, using trifluoroacetic acid in methanol. This was treated with periodate, which cleaves only between C-5 and C-6, to afford an aldehyde which reacted directly with K13CN to give a mixture of the D-arabino and L-xylo nitriles. The enriched nitriles were reduced with hydrogen in the presence of 5% Pd-carbon catalyst to a mixture of 6-aldehydo sugars. These were reduced with NaBH4 to a mixture of the two labeled methyl furanosides. Acid hydrolysis followed by ion-exchange chromatography on AG-50(Ca2+) resin at 65 degrees gave 10 in an overall yield of 16% from K13CN.
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PMID:Synthesis of 2-deoxy-D-arabino-(6-13C)hexose. 320 49

dl-2-(7,11-Dimethyl-3,7,11 - trans,trans-dodecatrienyl)-3-methyl-cyclopent-2-enol was prepared by reduction of the corresponding ketone. This tetraenol, on treatment with trifluoroacetic acid, underwent stereoselective cyclization to give dl-3,17-dimethyl-A-nor-D-homoestra-3,16-diene. This tetracyclic material was readily converted, by oxidative cleavage to the bicyclic triketo aldehyde followed by a double aldol cyclization, into dl-19-nor-16,17-dehydroprogesterone.
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PMID:Total synthesis of dl-19-nor-16,17-dehydroprogesterone. 525 14

Ovine rhodopsin was regenerated with 11-cis-[15-3H]retinal and cleaved in situ by Staphylococcus aureus V8 proteinase to give two membrane-bound fragments of Mr 27 000 (V8-L) and 12 000 (V8-S). After purification of the proteolysed complex by affinity chromatography with concanavalin A-Sepharose 4B, [3H]retinal was covalently linked to the protein by reduction with borohydride. The purified [3H]-retinyl V8-S fragment was cleaved with CNBr and trifluoroacetic acid, the resulting peptides resolved by gel filtration and the [3H]retinyl peptide sequenced. The protocol developed for the isolation and sequencing of this region of the ovine protein was applied directly, and reproducibly, to bleached and unregenerated porcine and equine opsins. Comparisons of the primary structures of the fragments reveals marked variation in the sequence immediately after the lysine residue shown in the ovine protein to be the attachment point for the aldehyde group of the chromophore. Mutable positions are localized in regions previously predicted as adopting nonregular or distorted conformations and hint at structural arrangements that may provide a better understanding of the spectral and functional properties of the visual pigment.
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PMID:Sequence variability in the retinal-attachment domain of mammalian rhodopsins. 637 Feb 31

A high-performance liquid chromatographic method has been developed for the determination of urinary tetrahydro-beta-carbolines. When standing tryptamine with formaldehyde and acetaldehyde under extraction conditions, the significant amounts of artefact 1,2,3,4-tetrahydro-beta-carboline (TBC) and 1-methyl-1,2,3,4-tetrahydro-beta-carboline (MTBC) were formed in a short time. Urine samples added with 2-ethyl-1,2,3,4-tetrahydro-beta-carboline (an internal standard) were treated with fluorescamine, and then with glycine, followed by serial solvent extractions. Such a pretreatment using two-step reactions removed a precursor (trypamine) by extracting its fluorescamine derivative, and enhanced the detection response by consuming excess fluorescamine. It solved the analytical problem that artefact TBC and MTBC are formed during analysis. Reversed-phase ion-pair chromatography using a C8-column and trifluoroacetic acid as a counter ion completed a base-line separation of three analytes within 10 min. The calibration graphs showed a good linearity in the range 0.1-50.0 ng ml-1 of urine samples spiked with standard TBC and MTBC. In the spike experiment, the recovery and relative standard deviation were almost 100% and less than 3.0%, respectively, for both TBC and MTBC. The proposed method enables the determination of the genuine urinary concentrations of TBC and MTBC without involving their artefacts.
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PMID:Determination of tetrahydro-beta-carbolines in urine by high-performance liquid chromatography with suppression of artefact formation. 769 79

The anti-HIV agent (+/-)-calanolide A (1) has been synthesized in a five-step approach starting with phloroglucinol [-->5-->6-->11-->18-->(+/-)-1], which includes Pechmann reaction, Friedel-Crafts acylation, chromenylation with 4,4-dimethoxy-2-methylbutan-2-ol, cyclization, and Luche reduction. Cyclization of chromene 11 to chromanone 18 was achieved by employing either acetaldehyde diethyl acetal or paraldehyde in the presence of trifluoroacetic acid and pyridine or PPTS. Luche reduction of chromanone 18 at lower temperature preferably yielded (+/-)-1. Reduction of chromone 12, synthesized by Kostanecki-Robinson reaction from chromene 11, failed to afford (+/-)-1. The synthetic (+/-)-1 has been chromatographically resolved into its optically active forms, (+)- and (-)-1. The anti-HIV activities for synthetic (+/-)-1, as well as resultant (+)- and (-)-1, have been determined. Only (+)-1 accounted for anti-HIV activity, which was similar to the data reported for the natural product, and (-)-1 was inactive.
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PMID:Synthesis, chromatographic resolution, and anti-human immunodeficiency virus activity of (+/-)-calanolide A and its enantiomers. 863 37

The novel 19-(cyclopropylamino)-androst-4-en-3,17-dione (5, CPA), a mechanism-based inhibitor of aromatase has been synthesized from the 10 beta-aldehyde intermediate (2). The key reaction was the trifluoroacetic acid-catalysed condensation of 2 with cyclopropylamine in refluxing toluene to give the 19-cyclopropylimine (3). Enzyme inhibition studies show that CPA is a time-dependent, irreversible inhibitor of human placental microsomal aromatase (Ki = 92 +/- = 2 nM). The inactivation of aromatase by CPA was NADPH-dependent and was protected by the presence of substrate testosterone (20 microns). In addition, the inactivation was not affected by the nucleophile, L-cysteine (0.5 mM), suggesting retention of the inhibitor in the enzyme's active site during the inactivation process.
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PMID:Novel 19-(cyclopropylamino)-androst-4-en-3,17-dione: a mechanism-based inhibitor of aromatase. 883 29

New solid-phase strategies have been developed for the synthesis of lidocaine (1) and procainamide (2) analogues, using backbone amide linker (BAL) anchoring. Both sets were prepared starting from a common resin-bound intermediate, followed by four general steps: (i) attachment of a primary aliphatic or aromatic amine to the solid support via reductive amination (as monitored by a novel test involving reaction of 2,4-dinitrophenylhydrazine with residual aldehyde groups); (ii) acylation of the resultant secondary amine; (iii) displacement of halide with an amine; and (iv) trifluoroacetic acid-mediated release from the support. A manual parallel strategy was followed to provide 60 novel compounds, of which two dozen have not been previously described. In most cases, initial crude purities were >80%, and overall isolated yields were in the 40-88% range.
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PMID:Solid-phase synthesis of lidocaine and procainamide analogues using backbone amide linker (BAL) anchoring. 1460 16

The solid-phase synthesis of 1,2,3,4-tetrahydroisoquinoline-3-carboxamides employing carboxyl-supported, o-alkylated tyrosine esters in a Pictet-Spengler reaction is described. Esterification of [4-(hydroxyphenyl)thiomethyl]polystyrene (Marshall resin) with ethers of N-BOC-L-tyrosine using diisopropylcarbodiimide (DIC) and 4-dimethylaminopyridine (4-DMAP) afforded the solid-supported ester derivatives. Removal of the BOC group with trifluoroacetic acid (TFA) afforded the carboxyl-supported tyrosine ester, which was then treated with paraformaldehyde and TFA to afford the desired solid-supported counterpart. Acylation of the secondary amine with arylsulfonyl chlorides followed by reaction with amines resulted in the formation of the desired 2-arylsulfonyl-7-alkoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxamides. Alternatively, the support-bound tetrahydroisoquinoline-3-carboxylate derivatives could be treated with an aldehyde and a reducing agent to give the corresponding support-bound tertiary amine. Exposure of these resin-bound products to amines afforded the corresponding 2-alkyl-7-alkoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxamides after cleavage from the resin. Alternative routes to the desired chemotypes, as well optimization of the conditions for the Pictet-Spengler reaction and the conditions for the acylation and reductive amination of the support-bound secondary amines, are also described.
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PMID:Solid-phase synthesis of 1,2,3,4-tetrahydroisoquinoline derivatives employing support-bound tyrosine esters in the Pictet-Spengler reaction. 1524 18

Sapphyrins are an important group of expanded porphyrins that show valuable anion binding characteristics. In this study, a "4 + 1" route to sapphyrin systems has been developed. Reaction of dialdehydes with a known tetrapyrrole intermediate 11b incorporating a bipyrrolic subunit afforded a wide range of sapphyrin-type products. The best conditions for these reactions involved carrying out the condensation of the dialdehydes with the tetrapyrrole in TFA-dichloromethane, followed by oxidation with dilute aqueous solutions of ferric chloride. A pyrrole dialdehyde reacted under these conditions to give sapphyrin in 50% yield, while furan and thiophene dialdehydes afforded the corresponding oxa- and thiasapphyrins in 66-90% yield. Pyrrole dialdehydes with fused phenanthrene or acenaphthylene rings also reacted with 11b to give the related phenanthro- and acenaphthosapphyrins in excellent yields. As was the case for acenaphthoporphyrins, the acenaphthosapphyrin gave longer wavelength absorptions than the corresponding phenanthrene fused structure, although the differences were not as marked as those seen in the porphyrin series. Reaction of 11b with 1,3-diformylindene gave a benzocarbasapphyrin in 38% yield, while a triformyl cyclopentadiene reacted with the tetrapyrrole to give a carbasapphyrin aldehyde in 7-12% yield. The free base carbasapphyrins were unstable but the monoprotonated hydrochloride salts could easily be isolated and characterized. Carbasapphyrins retain a strong diatropic ring current due to the presence of 22pi electron delocalization pathways. In the presence of trifluoroacetic acid, C-protonated dications are generated. Condensation of 1,3-azulenedicarbaldehyde with 11b gave an azulisapphyrin dihydrochloride salt in 35% yield, and this also showed a strong diatropic ring current. Addition of base gave the unstable free base form, while pyrrolidine formed an unstable adduct that showed an intense Soret band at 480 nm. These results demonstrate that many of the themes observed for modified porphyrins and carbaporphyrins also apply to the sapphyrin series, although in some cases reduced stability hampers these investigations.
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PMID:Synthesis of sapphyrins, heterosapphyrins, and carbasapphyrins by a "4 + 1" approach. 1557 66

An efficient synthesis of a fully functionalized tetracycle (A-B-C-H) 7 containing a 1,4-bridged 10-membered lactone was developed. Phenolic aldol condensation between 2-methylsesamol (15) and Garner's aldehyde provided the protected amino diol 16, which was converted to free amine 11 in excellent yield. A Pictet-Spengler reaction between 11 and ethyl glyoxylate under carefully controlled conditions (LiCl, toluene, 1,1,1,3,3,3-hexafluoro-2-propanol, room temperature) provided the acid-sensitive tetrahydroisoquinoline (18) in high yield, which was converted to the amino alcohol 9. Enantioselective alkylation of a glycine template in the presence of a catalytic amount of chiral cinchonidium salt was the key step for the access of enantiomerically pure amino aldehyde 10. Union of the two fragments 9 and 10 via oxazolidine intermediate afforded amino nitrile 39, which upon esterification of the primary alcohol with (R)-N-(S-4,4',4' '-trimethoxyltrityl) Cys (42) afforded 43. Cyclization of 43 (1% trifluoroacetic acid in trifluoroethanol) provided compound 44 by a domino process involving (a) unmasking of the S-trimethoxytrityl group, (b) fragmentation of dioxane assisted by an electron-rich aromatic ring, and (c) formation of a 1,4-bridged 10-membered lactone via formation of a sulfide linkage. Treatment of 7, obtained in two steps from 44b, under acidic conditions (0.5% methyl sulfonic acid in acetonitrile) afforded the pentacyclic compound 51 via fragmentation of the 10-membered cyclic sulfide followed by an intramolecular Pictet-Spengler reaction.
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PMID:Synthetic studies toward ecteinascidin 743. 1590 18


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