7-Chloroquinoline: a versatile intermediate for the synthesis of 7-substituted quinolines

A practical synthesis of 7-mono-substituted quinolines has been achieved. Selective reduction of the inexpensive commercial reagent 4,7-dichloroquinoline affords 7-chloroquinoline, which has been converted into more complex 7-mono-substituted quinolines through a series of Pd-catalyzed cross coupling reactions. These studies include the first examples of Suzuki reactions for the preparation of 7-mono-substituted quinolines as well as the first application of the Sonagashira reaction for the synthesis of 7-substituted quinolines. This strategy has been extended to the preparation of 2,7-di-substituted quinolines.     

Enantioselective formal total synthesis of the antitumor macrolide bryostatin 7

A new enantioselective synthesis of Masamune's AB fragment (1) for bryostatin 7 is described. Key steps in the new route include a Meerwein-Ponndorf-Verley reduction to set the O(7) stereocenter and an alkylative union between the dithiane 6 and iodide 5 to construct the C(9)-C(10) bond. Because we have previously published a synthesis of Masamune's C-ring phenyl sulfone 2, our new route to 1 constitutes a formal total synthesis of bryostatin 7; it also corrects the previously reported spectral data for 1 in CDCl3.     

7-Substituted 8-aza-7-deazaadenosines for modification of the siRNA major groove

Here we describe the synthesis of new 7-substituted 8-aza-7-deazaadenosine ribonucleoside phosphoramidites and their use in generating major groove-modified duplex RNAs. A 7-ethynyl analog leads to further structural diversification of the RNA via post-automated RNA synthesis azide-alkyne cycloaddition reactions. In addition, we report preliminary studies on the effects of eight different purine 7-position modifications on RNA duplex stability and pairing specificity. Finally, the effect on RNAi activity of this type of modification at eight different positions in an siRNA guide strand has been explored. Analogs were identified with large 7-position substituents that maintain adenosine pairing specificity and are well-tolerated at specific positions in an siRNA guide strand.     

Transition-metal-free access to 7-azaindoles

A novel method for transition-metal-free synthesis of 7-azaindoles is developed through a one-pot synthesis involving amination of pyridine N-oxides and intramolecular enamine formation. Remarkable features of the method include simple operation, mild reaction conditions, wide substrate scope, and easily accessible starting materials.     

Some reactions of 1,3,5-Triaza-7-phosphaadamantane and its 7-Oxide

The synthesis of 1,3,5,7-triazaphosphocine and 1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane derivatives via nitration, nitrosation and acetylation of 1,3,5-triaza-7-phosphaadamantane and its 7-oxide is reported. A comparison of the reactions of the triazaphosphaadamantane with the analogous reactions of hexamine is made.     

A Novel and Efficient Synthesis of (6R,7R)-7-Amino-3-hydroxymethyl Cephalosporanic Acid: A Versatile Precursor of Cefuroxime Acid

Abstract

A novel process has been developed for the synthesis of (6R,7R)-7-amino-3-hydroxymethyl cephalosporanic acid (7-AHCA) using a combination of reagents [triethyl amine/tetrabutyl ammonium hydroxide (TBAH)] at ambient temperature, with improved yield. This intermediate was exploited for the synthesis of cefuroxime acid and its sodium salt.     

Synthesis and the structure of tribromo(7-bromobicyclo[4.1.0]hept-7-yl)germane

A general procedure was developed for the synthesis of halocyclopropylgermanes. This procedure was used for the preparation of tribromo(7-bromobicyclo[4.1.0]hept-7-yl)germane. The molecular structure was established by GLC-mass spectrometry, ¹H NMR spectroscopy, and X-ray diffraction analysis.     

Reaction of 6(7)-acyl-and 6(7)-formylperimidines with 1,3,5-triazines in poly-phosphoric acid

A method has been developed for the synthesis of 1,3,7-triazapyrenes using the reaction of 6(7)-formyl-and 6(7)-benzoylperimidines with 1,3,5-triazines in PPA. Under these conditions, 6(7)-formylperimidine reacts with 2,4,6-trimethyl-1,3,5-triazine to give 6-hydroxy-1,3-diazapyrene. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1080–1084, July, 2008.     

Chemoenzymatic total synthesis of paecilocin A and 3-butyl-7-hydroxyphthalide

A highly enantioselective total synthesis of paecilocin A and 3-butyl-7-hydroxyphthalide is described. The key steps involved in this synthesis are enzymatic kinetic resolution and Alder–Rickert reaction.     

Preparative Synthesis of 7-Carboxy-2-R-isoindol-1-ones

A preparative method for the synthesis of 7-carboxy-2-R-isoindol-1-ones was developed on the basis of the [4+2] cycloaddition of secondary furfurylamines to maleic anhydride.     

Total synthesis of calystegine A7

A straightforward chiral pool synthesis for the glycosidase inhibitor calystegine A₇ (isolated from Lycium chinense) from methyl α-d-glucopyranoside is described. Keysteps of this synthesis include a ultrasound assisted Zn-mediated tandem ring opening reaction followed by a Grubbs' catalyst mediated ring closure metathesis.     

Synthetic applications of organoselenium reagents: synthesis of epi-7-hydroxymyoporone

A synthesis of racemic epi-7-hydroxymyoporone is described. The dianion prepared from phenyl propargyl selenide is the key reagent for the carbon-carbon bond forming reactions.     

Synthesis of novel substituted 3,8,11-triazaspiro[5,6]dodecan-7-ones

A synthesis of novel substituted 3,8,11-triazaspiro[5,6]dodecan-7-ones using a combination of solution-phase and solid-phase chemistries is described. A solution-phase approach was used to produce a key piperidine intermediate that was then incorporated into a solid-phase synthesis. The combined synthetic strategy was applied to provide a series of substituted 3,8,11-triazaspiro[5,6]dodecan-7-ones in good yield and high purity.     

Aporphines 10. Approaches to the synthesis of 7-hydroxyaporphines : Stereoselective synthesis of (±)-10,11-dimethoxy-7-oxoaporphine, (±)-7-hydroxyaporphine and (±)-7-hydroxynoraporphine

A new method for the stereoselective synthesis of 7-hydroxyaporphine (3a) and 7-hydroxynoraporphine (3b) via the 4-oxazolin-2-one 20 as a protecting group has been developed. Pschorr cyclization of 20 and hydrolysis of the oxazoloaporphine 21 with trifluoroacetic acid led exclusively to the dehydronoraporphine 22. Reduction of 21 with LAH gave 3a and treatment of 21 with methyllithium gave 3b. The synthesis of 10,11-dimethoxy-7-oxoaporphine (2) involving a Reissert alkylation-Pschorr cyclization sequence has been achieved.     

A facile synthesis of isoflavone 7-O-glucuronides

An efficient method is presented for the synthesis of isoflavone 7-glucuronides using a N-(4-methoxyphenyl)-trifluoroacetimidate glucuronsyl donor. A 4-hexanoyl derivative of the isoflavone is used in the coupling reaction, both for protection and to improve solubility. These glucuronides are the human metabolites of estrogenic dietary isoflavones, but their biological activity and pharmacokinetics have yet to be established as until now there were no good methods for their synthesis.     

An easy access to 7-methyl-2-naphthalenecarbonitrile

A practical and cost-effective procedure has been developed for the synthesis of 7-methyl-2-naphthalenecarbonitrile, the precursor of the anticoagulant agents YM-60828 or YM-96765. This new route generates the key intermediate in only two steps from readily available 3-cyanopropionaldehyde dimethyl acetal and m-tolualdehyde, without requiring chromatographic purification. The synthesis involves condensation of the cyano derivative with the aldehyde and subsequent cyclodehydration.     

Asymmetric alpha-alkylation of N'-tert-butanesulfinyl amidines. Application to the total synthesis of (6R,7S)-7-amino-7,8-dihydro-alpha-bisabolene

A highly diastereoselective alpha-alkylation of N'-tert-butanesulfinyl amidines has been developed along with methods for converting the alkylation products to enantiomerically enriched amines that incorporate both alpha- and beta-stereocenters. The utility of this chemistry is further demonstrated by the first asymmetric synthesis of the antimicrobial marine natural product (6R,7S)-7-amino-7,8-dihydro-alpha-bisabolene.     

7-氮杂吲哚N-氧化物的区域选择性脱氧硫醚化反应

本文开发了一种3-硫代-7-氮杂吲哚衍生物的合成方法。研究发现,在30%的I2的催化作用下,磺酰肼和7-氮杂吲哚N-氧化物在正丁醇中110 °C条件下反应以53%-86%的产率得到硫醚化产物。该反应有较好的区域选择性和底物适应性。并具有反应时间较短,绿色环保和操作简便等优点。     

Novel 7-substituted quinolone antibacterial agents. Synthesis of 7-alkenyl,cycloalkenyl, and 1,2,3,6-tetrahydro-4-pyridinyl-1,8-naphthyridines

A convergent synthesis of 1,8-naphthyridine antibacterials bearing a carbon-carbon bonded, acyclic or cyclic vinyl substituent at the C-7 position has been achieved. The synthetic methodology is based upon the palladium-catalyzed cross coupling of a 7-chloro-1,8-naphthyridine with an appropriately substituted organotin reagent.     

Synthesis of some 7-substituted-2,4,8(1H,3H,7H)pyrimido[5,4-d]pyrimidinetriones

A synthesis of 2,4,8-pyrimido[5,4-d]pyrimidinetriones under mild conditions from ethyl 5-ethoxymethyleneamino-orotate allows the introduction of a variety of substituents regiospecifically into the 7-position. The 7-methyl and 7-benzyl derivatives were methylated with trimethyl phosphate to the 1,3,7-trialkyl derivatives.