Preparation and characterization of 2-silanorbornanes

Cremer, Sheldon E.; Blankenship, Craig

doi:10.1021/jo00348a004

Cited by 19 publications

(7 citation statements)

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“…The bisindole 22 with its unsubstituted butane-1,4-diyl linker was prepared in excellent yield by reaction of the sodium anion Desilylation of 18, and acetylation, gave the allylic acetate 10 19 (Scheme 2) whose relative configuration was confirmed by the observation of diagnostic NOE measurements (Fig. 1); the allylic acetate 19 underwent smooth palladium-catalysed substitution with the indole-3-carboxyaldehyde (17) to give the required meso bisindole 20 (entry 7, Table 1). The relative configuration of 20 was confirmed by X-ray crystallography 18 in >90% yield (entries 5-6, Table 1).…”

Section: Strategy A: Preparation Of Intermediates For Macrocyclisatio...mentioning

confidence: 97%

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Evaluation of alternative approaches for the synthesis of macrocyclic bisindolylmaleimides

Bartlett

Nelson

2004

Org. Biomol. Chem.

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Approaches for the synthesis of macrocyclic bisindolylmaleimides, in which the indole nitrogens are linked with a tether, are described. Two alternative approaches were investigated: macrocyclisation in either the 'southern' (by adding the tether to the bisindolylmaleimide ring system) or the 'northern' district. With two-, three- and four-atom tethers, both of these approaches were unsuccessful for a wide range of attempted macrocyclisation reactions (palladium-catalysed pi-allyl substitution, ring-closing metathesis, McMurry reaction, iodocyclisation, formation of a silylene derivative, substitution of an alpha,omega-disubstituted electrophile). The failure of all of these reactions was ascribed to the strained nature of the target ring system. However, with longer tethers (six to ten atoms), the macrocycles could prepared using either a ring-closing metathesis reaction or by substitution of an alpha,omega-dibromide). Fourteen successful macrocyclisation reactions are described; deprotection gave eleven macrocyclic bisindolylmaleimides in which an imide substituent had been removed.

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Section: Strategy A: Preparation Of Intermediates For Macrocyclisatio...mentioning

confidence: 97%

“…The alkylation of the bisindolylmaleimide 29 was studied with a range of simple electrophiles (Scheme 6 and Table 2). Although most alkylations of 29 were routine (entries 1-4, Table 2), cyclopent-3-enylation 16,17 the monosubstituted bisindolylmaleimide 38e and recovered starting material (29) (entries 5b-c).…”

Section: Scheme 4 Schemementioning

confidence: 99%

Evaluation of alternative approaches for the synthesis of macrocyclic bisindolylmaleimides

Bartlett

Nelson

2004

Org. Biomol. Chem.

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“…9 The latter process afforded a 3:1 mixture of trans:cis epoxides from which the trans-isomer was isolated in 40% yield following silica gel column chromatography. Compound 4a was converted to the corresponding iodide 10 and then to the diisopropyl phosphonate ester in a standard Arbuzov reaction. We have found throughout this work that diisopropyl phosphonates give generally cleaner reactions than the corresponding ethyl or methyl Several other carbocyclic phosphonic acids were synthesised according to Scheme 3 and Scheme 4.…”

Section: Figurementioning

confidence: 99%

A Flexible, Efficient Synthesis of (±)-Carbocyclic Phosphonic Acid Nucleoside Derivatives

Wainwright¹,

Maddaford²,

Bissell³

et al. 2005

Synlett

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An efficient and flexible synthesis of cyclopentane and hydroxylated cyclopentane phosphonic acid analogues is described.The key step involves the opening of an epoxide with either a nucleoside base or a selenyl anion to access the target molecules.Chemotherapies based on the administration of analogues of nucleosides and deoxynucleosides 1 have proved successful against a range of cancers and viral infections such as HIV, cytomegalovirus, and herpes virus. 1 In each case, intracellular processing of the nucleoside to its triphosphate 2 generates the active form of the nucleoside. 2 This phosphorylation sequence is often stepwise, and performed by more than one cellular kinase, and the initial formation of the nucleoside monophosphate is often the most difficult step in the sequence. Strategies to facilitate or bypass this first phosphorylation step have included the use of prodrugs of the pre-formed monophosphate. 3 Phosphonic acids 3 are rather more chemically stable analogues of the monophosphate which in some cases can still undergo phosphorylation and generate effective mimics of a nucleoside triphosphate ( Figure 1). 4 Figure 1Nucleosides, nucleoside triphosphates, and carbocyclic phosphonic acid nucleoside mimics.We have been investigating synthetic procedures which would allow us to access a range of phosphonic acid analogues of carbocyclic nucleosides. 5 Herein, we wish to report a flexible synthesis of hydroxy, dihydroxy and dideoxy versions using an efficient epoxide-opening strategy outlined in Scheme 1. Carbocyclic ribose analogues have been synthesised in a variety of ways, usually starting with ribose itself or a substituted cyclopentane derivative. 6 Such routes could be adapted to access phosphonic acids, however, we wished to maximise the flexibility of our route, and chose to synthesise all targets via the readily prepared epoxy-alcohol 4. In this strategy, nucleoside bases can be added to the meso-trans-epoxy-phosphonylmethyl cyclopentane 5 to generate directly 3¢-deoxycarbocyclic nucleosides 7. Conversely, the cis-epoxyphosphonylmethyl cyclopentane 6 could be converted to an allyl species onto which bases could be appended using Pd-p-allylation chemistry, 7 providing access to a range of ribose 10, arabinose 11, cyclopentane 9 and cyclopentene 8 analogues. This article describes how this strategy was put into practice.Scheme 1 An epoxide-opening strategy to access cyclopentene 8, cyclopentane 9, hydroxycyclopentane 7, cis-dihydroxycyclopentane 10 and trans-dihydroxycyclopentane 11 phosphonic acid nucleoside mimics.The trans-epoxy-alcohol 4a 8 was synthesised in six straightforward steps (Scheme 2) from dimethyl malonate, by a sequence of allylation, RCM, 8a saponification, reduction, alcohol silyl-protection and a trans-selective epoxidation. 9 The latter process afforded a 3:1 mixture of trans:cis epoxides from which the trans-isomer was isolated in 40% yield following silica gel column chromatography. Compound 4a was converted to the corresponding iodide 10 and then to the diisopropyl phosp...

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“…The 1 H and 13 C NMR spectra of 24 were identical to those previously reported. [41] General Procedure 2 (GP2) for the PdCl 2 (dppf)-Catalyzed Cross Coupling: A solution of (cyclopenten-4-yl)magnesium bromide (15) freshly prepared from 4-bromocyclopentene (14) (45 mmol) and magnesium (50 mmol) in anhydrous Et 2 O (30 mL) was added via a cannula in one portion to a mixture of the aryl halide 16 (18 mmol) and the catalyst (3 mol %) in anhydrous Et 2 O (100 mL) at ambient temp. Upon coupling of the aryl bromides, the initial orange color rapidly changed to yellow after 10 min of stirring, then to green or brown.…”

Section: Preparation Of Bromides 14 and 24 General Procedures 1 (Gp1)mentioning

confidence: 99%

Novel Liquid Crystalline Compounds Containing Bicyclo[3.1.0]hexane Core Units

et al. 2004

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Keywords:Cross-coupling / Cycloadditions / Liquid crystals / Small ring systems / Structure elucidation Additions of ethyl or tert-butyl diazoacetates to 4-substituted cyclopentenes 6 and 17 under dirhodium tetraacetate/tetraoctanoate catalysis led to mixtures of tert-butyl endo, exoand exo,exo-3-carboxyl(aryl)bicyclo[3.1.0]hexane-6-carboxylates 7 and 18 in yields of 54−90% from which exo,exodiastereomers were isolated in yields of 39−63%. Diester exo,exo-7 was saponified and converted into diaryl diesters exo,exo-9a,b in overall yields of 42 and 46%, respectively. The esters exo,exo-18 were reduced to the corresponding hydroxymethyl derivatives, these were transformed to the iodomethyl compounds which in turn were coupled with various alkylmagnesium halides, via Li 2 CuCl 4 catalysis, to give 3-aryl-6-alkylbicyclo[3.1.0]hexyl derivatives exo,exo-21 in overall yields of 72−83%. Fluorinated 3-(2-arylethyl)-6-pentylbicyclo[3.1.0]hexane exo,exo-32 could be prepared in five steps from 4-ethoxy-2,3-difluorobenzaldehyde 26a ad-

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Preparation and characterization of 2-silanorbornanes

Cited by 19 publications

References 0 publications

Evaluation of alternative approaches for the synthesis of macrocyclic bisindolylmaleimides

Evaluation of alternative approaches for the synthesis of macrocyclic bisindolylmaleimides

A Flexible, Efficient Synthesis of (±)-Carbocyclic Phosphonic Acid Nucleoside Derivatives

Novel Liquid Crystalline Compounds Containing Bicyclo[3.1.0]hexane Core Units

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