- Samarium Diiodide Catalyzed Radical Cascade Cyclizations that Construct Quaternary Stereocenters
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SmI 2 -catalyzed radical cascade cyclizations were used to generate complex carbocyclic products bearing quaternary stereocenters with high selectivity. Bicyclic scaffolds containing four contiguous stereocenters and one quaternary stereocenter
- He, Qiong,Huang, Huan-Ming,Procter, David J.
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- Synthesis of derivatives of 1,2,6-trisubstituted-4-piperidones
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Robinson-Schopf cyclisation was used to prepare several 1,2,6-trisubstituted-4-piperidones: 1,2,6-trimethyl-4-piperidone, tricyclic ketones 2 and 3 derivatives of coccinelline. In the case of 1,2,6-trimethyl-4-piperidone, a mixture of the trans and cis compounds 4 and 1 was obtained. The pure cis compound was prepared by another route.
- Langlois,Yang,Soulier,Florac
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- Four nucleophilic additions to alkenynedioic acid derivatives in tandem; Efficient one-pot synthesis of bicyclo[4.2.0]octenols
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When alkenynedioic acid derivatives were treated with a Grignard reagent, tandem cyclization and the incorporation of two molecules of the Grignard reagent occurred to give stereodefined bicyclo[4.2.0]octenols via four nucleophilic additions.
- Hata, Takeshi,Imade, Haduki,Urabe, Hirokazu
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supporting information; scheme or table
p. 2450 - 2453
(2012/07/27)
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- Synthesis of acyclic nucleoside derivatives
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Methods and novel intermediates of the formula: wherein R6 and R7 are lower alkyl or benzyl or R6 and R7 taken together are —CH2CH2—, —CH2CH2CH2— or —CH2CH2CH2CH2CH2—, R8 is C1-C21 alkyl or a C2-C21 monounsaturated alkenyl, which may optionally be substituted with substitution substituents independently selected from the group consisting of hydroxy, C1-C6 alkyl, C1-C6 alkoxy, C1-C6 alkoxy C1-C6 alkyl, C1-C6 alkanoyl, amino, halo, cyano, azido, oxo, mercapto and nitro, and R9 is an alcohol protecting group. The intermediates are useful for the preparation of acyclic nucleoside derivatives of the formula: where one of R1 and R2 is an amino acid acyl group and the other of R1 and R2 is a —C(O)C3-C21 saturated or monounsaturated, optionally substituted alkyl and R3 is OH or H; or a pharmaceutically acceptable salt thereof.
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- Regioselective alkylation of guanines using 2-acetoxytetrahydrofurans
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Reaction of silylated guanine derivatives with 2-acetoxy-4-benzoyloxymethyltetrahydrofuran in DMF or NMP resulted in selective N-9 alkylation. This was used as the basis for a regioselective synthesis of the anti-viral agents famciclovir and penciclovir.
- Geen, Graham R.,Kincey, Peter M.,Spoors, P. Grant
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p. 1781 - 1784
(2007/10/03)
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- Asymmetric Pauson-Khand cyclizations of 1-sulfinylenynes
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The use of sulfoxides as chiral auxiliaries in intramolecular Pauson-Khand (PK) reactions is described. In particular, the tert-butylsulfinyl group acts as a very efficient chiral auxiliary in intramolecular PK reactions of 1-sulfinyl- 1,6-enynes. As the
- Carretero,Adrio
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p. 1888 - 1896
(2007/10/03)
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- Synthesis of 1-p-tolysulfinyl-1,3-dienes by intramolecular heck reactions
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The first examples of the synthesis of 1,3-dienyl sulfoxides by Heck reactions are described. Both racemic and enantiomerically pure exocyclic 1- p-tolylsulfinyl-1,3-dienes 1 are readily prepared by the intramolecular Heck reaction of their corresponding vinyl iodides in the presence of Pd(OAc)2 as catalyst and Ag2CO3 as base. (C) 2000 Elsevier Science Ltd.
- Mar Segorbe,Adrio, Javier,Carretero, Juan C.
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p. 1983 - 1986
(2007/10/03)
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- The 2-(N,N-dimethylamino)phenylsulfinyl group as an efficient chiral auxiliary in intramolecular heck reactions
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(Matrix presented) The synthesis, reactivity, and stereochemical behavior of differently substituted iodoalkenyl α,β-unsaturated sulfoxides in intramolecular Heck reaction is described. Particularly, the 2-(N,N-dimethylamino)phenylsulfinyl group is demons
- Buezo, Nuria Diaz,Mancheno, Olga Garcia,Carretero, Juan C.
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p. 1451 - 1454
(2007/10/03)
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- EINE NEUE SYNTHESE VON VINBLASTIN-DERIVATEN III. SYNTHESE UND REAKTIONEN VON 21,Nb-SECO-CLEAVAMIN-DERIVATEN ALS VORLAUFER ZU 20'-DEETHYL-20'-DEOXYVINBLASTIN UND (+/-)-16α-METHOXYCARBONYL-20-DEETHYL-15,20-DIHYDROCLEAVAMIN
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In a new concept for the synthesis of 20'-deethyl-20'deoxyvinblastine, Nb-seco-cleavamine derivatives 1a,2a are possible precursors.For the synthesis of these compounds the indolizino indoles 8I,II were treated with benzyl chloroformate/aq. sodium
- Schill, Gottfried,Priester, Claus Ulrich,Windhovel, Udo Frank,Fritz, Hans
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p. 3747 - 3764
(2007/10/02)
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- Synthesis and Structure-Activity Relationships of Series of Aminopyridazine Derivatives of γ-Aminobutyric Acid Acting as Selective GABA-A Antagonists
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We have recently shown that an aryloaminopyridazine derivarive of GABA, SR 95103 , is a selective and competitive GABA-A receptor antagonist.In order to further explore the structural requirements for GABA receptor affinity, we synthesized a series of 38 compounds by attaching various pyridazinic structures to GABA or GABA-like side chains.Most of the compounds displaced GABA from rat brain membranes.All the active compounds antagonized the GABA-elicited enhancement of diazepam binding, strongly suggesting that all these compounds are GABA-A receptor antagonists.None of the compounds that displaced GABA from rat brain membranes interacted with other GABA recognition sites (GABA-B receptor, GABA uptake binding site, glutamate decarboxylase, GABA-transaminase).They did not interact with the Cl- ionophore associated with the GABA-A receptor and did not interact with the benzodiazepine, strychnine, and glutamate binding sites.Thus these compounds appear to be specific GABA-A receptor antagonists.In terms of structure-activity, it can be concluded that a GABA moiety bearing a positive charge is necessary for optimal GABA-A receptor recognition.Additional binding sites are tolerated only if they are part of a charge-delocalized amidinic or guanidinic system.If this delocalization is achieved by linking a butyric acid moiety to the N(2) nitrogen of a 3-aminopyridazine, GABA-antagonistic character is produced.The highest potency (ca.250 times bicuculline) was observed when an aromatic ? system, bearing electron-donating substituents, was present on the 6-position of the pyridazine ring.
- Wermuth, Camille-Georges,Bourguignon, Jean-Jacques,Schlewer, Gilbert,Gies, Jean-Pierre,Schoenfelder, Angele,et al.
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p. 239 - 249
(2007/10/02)
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- Unusual Absence of β+1-Cleavage in Functionalised Esters
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An unusual absence of β+1-cleavage (absence of McLafferty fragment) in functionalised derivatives (Ia-c; IIa, b) of malonic acid under electron impact is reported.This observation is of intrinsic importance where McLafferty fragmentation is used as a diagnostic pathway for the identification of compounds bearing aldehyde and acetal functional groups.
- Neelakantan, Parvathi,Rao, Nagabhushan,Bhalerao, U. T.,Thyagarajan, G.
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