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Paul R Hanson

Publications and source records attributed to Paul R Hanson.

18 recordsLinked to original sources
PubMed2006

Design, synthesis, and antiproliferative and CDK2-cyclin a inhibitory activity of novel flavopiridol analogues.

The design and synthesis of a small library of 8-amidoflavone, 8-sulfonamidoflavone, 8-amido-7-hydroxyflavone, and heterocyclic analogues of flavopiridol is reported. The potential activity of these compounds as kinase inhibitors was evaluated by cytotoxicity studies in MCF-7 and ID-8 cancer cell lines and inhibition of CDK2-Cyclin A enzyme activity in vitro. The antiproliferative and CDK2-Cyclin A inhibitory activity of these analogues was significantly lower than the activity of flavopiridol. Molecular docking simulations were carried out and these studies suggested a different binding orientation inside the CDK2 binding pocket for these analogues compared to flavopiridol.

Adenosine Triphosphate↗
PubMed2006

Divalent activation in temporary phosphate tethers: highly selective cuprate displacement reactions.

Desymmetrization of a readily derived pseudo-C(2)-symmetric monocyclic phosphate via highly diastereoselective anti-S(N)2' allylic displacement reactions is reported. This method utilizes of a wide variety of zinc-derived organocuprates to afford E-1,2-syn-configured phosphate acid building blocks. Extension of this protocol to unsymmetric monocyclic phosphates exclusively yields 1,2-anti-configured products. Within this study, stereoelectronic factors, coupled with allylic strain, ultimately govern regio- and diastereoselective cuprate reactions, further substantiating the Corey mechanism for organocuprate additions into allylic esters. [reaction: see text]

Alcohols↗
PubMed2006

Temporary phosphate tethers: a metathesis strategy to differentiated polyol subunits.

[reaction: see text] Studies probing reactivity and selectivity of cross metathesis (CM) with an exocyclic olefin in a P-chiral bicyclo[4.3.1]phosphate triester are described. Studies have revealed a Type III CM reactivity pattern for the exocyclic olefin within this phosphate triester. This versatile method allows for simple, selective manipulation of a P-chiral building block en route to advanced polyol subunits.

Alkenes↗
PubMed2005

P-heterocyclic building blocks: application to the stereoselective synthesis of P-sugars.

A strategy relying on the utilization of stereoselective additions to allyldiphenylphosphonate esters and subsequent ring-closing metathesis (RCM) to access P-chiral P-heterocyclic building blocks for the synthesis of phosphono sugars is described. These building blocks possess several attractive components, including the following: (i) P(2) and C(6) stereogenic centers for directing stereoselective transformations; (ii) an activated C(3) methylene group that promotes base-mediated olefin transposition to generate vinyl phosphonates available for further stereoselective reactions; and (iii) a P(2)-stereogenic center containing an exchangeable phosphonate ester armed to attenuate the "stereochemical environment" at phosphorus. Taken collectively, these attributes contribute to a concise method for the stereoselective synthesis of an array of P-sugars.

Carbohydrates↗
PubMed2005

Multivalent activation in temporary phosphate tethers: a new tether for small molecule synthesis.

[reaction: see text]. A new tether for small molecule synthesis is reported. This functionally active tether mediates the desymmetrization of a pseudo-C(2)-symmetric tris-allylic phosphate triester to generate a P-chiral bicyclo[4.3.1]phosphate containing ample steric and stereoelectronic differentiation for investigating chemo-, regio-, and stereoselective transformations. Overall, the method reported herein demonstrates a fundamentally new role of phosphates in synthesis and provides differentiated polyol building blocks for use in natural product synthesis.

Biological Products↗
PubMed2005

Multipolymer solution-phase reactions: application to the Mitsunobu reaction.

The realization of the first polymer-on-polymer Mitsunobu reaction, in which a polymeric phosphine is used simultaneously with a polymeric azodicarboxylate, is reported. This strategy employs the use of soluble oligomers generated from ring-opening methathesis polymerization. 31P NMR analysis revealed that the two polymers were interacting to generate the Mitsunobu products. Application to several substrates, as well as comparison experiments with other polymeric reagents, is described.

Biological Factors↗
PubMed2004

High-load, soluble oligomeric carbodiimide: synthesis and application in coupling reactions.

A facile preparation of a high-load, soluble oligomeric alkyl cyclohexylcarbodiimide (OACC) reagent via ROM polymerization from commercially available starting materials is described. This reagent is exploited as a coupling reagent for esterification, amidation, and dehydration of carboxylic acids (aliphatic and aromatic) with an assortment of alcohols (aliphatic primary, secondary, and benzylic), thiols, phenols, and amines (aliphatic primary, secondary, benzylic, and aromatic/anilines), respectively. Following the coupling event, precipitation with an appropriate solvent (Et(2)O, MeOH, or EtOAc), followed by filtration through a SPE provides the products in good to excellent yield and purity.

Carbodiimides↗
PubMed2004

Development of high-load, soluble oligomeric sulfonate esters via ROM polymerization: application to the benzylation of amines.

The development of high-load, soluble oligomeric sulfonate esters, generated via ROM polymerization, and their utility in the facile benzylation of an array of amines is reported. These polymeric sulfonate esters exist as free-flowing powders, are stable at refrigerated temperatures, and are readily dissolved in CH(2)Cl(2). Following the benzylation event, purification is attained via simple filtration, followed by solvent removal to deliver the desired benzylated product in good to excellent yield and high purity. [structure: see text]

Alkylating Agents↗
PubMed2003

High-load, ROMP-generated oligomeric bis-acid chlorides: design of soluble and insoluble nucleophile scavengers.

[reaction: see text] An efficient strategy for scavenging a host of nucleophiles utilizing an oligomeric bis-acid chloride (OBAC), generated from the ROM polymerization of trans-bicyclo[2.2.1]hept-5-ene-2,3-dicarbonyl dichloride, is described. The reactivity and high load of the OBAC reagent is exploited in the scavenging of amines, alcohols, and thiols that are present in excess following a common benzoylation event. Following the scavenging event, these oligomers can be precipitated with EtOAc and filtered (SiO(2)), leaving benzoylated nucleophiles in excellent yield and purity.

Acids↗
PubMed2003

ROMP-generated oligomeric sulfonyl chlorides as versatile soluble scavenging agents.

[reaction: see text] A new method for homogeneous nucleophilic scavenging employing oligomeric sulfonyl chloride (OSC) reagents is described. The method utilizes OSC to rapidly scavenge a variety of amines that are present in excess. The OSC reagents are generated from ROM polymerization of 2-chlorosulfonyl-5-norbornene utilizing the second generation Grubbs catalyst to produce oligomers of varying size as stable, free-flowing powders. Following the scavenging event, these oligomers are precipitated with ethyl acetate leaving products in excellent yield and purity.

Amines↗
PubMed2003

Ring-opening metathesis phase-trafficking (ROMpt) synthesis: multistep synthesis on soluble ROM supports.

The use of ring-opening metathesis (ROM) oligomers as soluble supports for a multistep reaction sequence is described. A Mitsunobu reaction followed by an in situ ROMP-mediated phase-trafficking purification is utilized to generate soluble ROM oligomers that are isolated via precipitation with methanol. Once formed, the ROM oligomers serve as soluble supports for further solution-phase reactions, including a ring-closing metathesis. After each step, the support-bound products are isolated by precipitation with a suitable solvent. [reaction--see text]

Chemical Precipitation↗
PubMed2002

A concise route to structurally diverse DMP 323 analogues via highly functionalized 1,4-diamines.

[reaction: see text] The utility of functionalized 1,4-diamines, produced via a temporary phosphorus tether (P-tether)/ring-closing metathesis (RCM)/hydrolysis sequence, is demonstrated in the synthesis of structurally diverse DMP 323 analogues. These 1,4-diamines are transformed into various seven-membered heterocycles via insertion of the appropriate nuclei "X". Subsequent derivatization generates heterocyclic diols that are similar in structure to DMP 323, a notable member of a class of highly potent inhibitors of HIV protease.

Alcohols↗
PubMed2002

Conformationally constrained alpha-boc-aminophosphonates via transition metal-catalyzed/curtius rearrangement strategies.

A transition metal-catalyzed/Curtius rearrangement sequence toward the development of conformationally constrained alpha-Boc-aminophosphonates 2-6 is described. An approach using the versatile tert-butylphosphonoacetate moieties 1a and 1b to derive an array of mono- and bicyclic alpha-Boc-aminophosphonate systems is presented. Conformational constraint is incorporated using either the ring-closing metathesis reaction catalyzed by the first generation Grubbs catalyst or intramolecular cyclopropanation mediated by Rh2(OAc)4. Using the tert-butyl ester functionality in 1a or 1b as a potential amino group, the Curtius rearrangement provides an efficient route toward the target alpha-Boc-aminophosphonates.

Amines↗
PubMed2002

Double diastereoselective intramolecular cyclopropanation to P-chiral [3.1.0]-bicyclic phosphonates.

[reaction: see text] A double diastereotopic differentiation strategy on a phosphonoacetate template is described. The approach utilizes Rh(2)(OAc)(4)-catalyzed intramolecular cyclopropanation (ICP) employing the (R)-pantolactone auxiliary in the ester functionality of the phosphonoacetate. The olefinic diastereofacial selectivity is governed by inherent electronic and steric interactions in the reacting carbene intermediate, while the group selectivity is dictated by the chiral auxiliary. This approach is being developed as an effective method to access bicyclic P-chiral phosphonates.

Catalysis↗
PubMed2002

Scavenge-ROMP-filter: a facile strategy for soluble scavenging via norbornenyl tagging of electrophilic Reagents.

[reaction: see text] A new "chemical tagging" method for homogeneous electrophilic scavenging is described. The method utilizes 5-norbornene-2-methanol to scavenge/tag a variety of electrophiles that are present in excess. Once tagging is complete, the crude reaction mixture is subjected to a rapid ROM polymerization event utilizing the second generation Grubbs catalyst. This process yields a polymer that can be precipitated with methanol or ether/hexane, leaving products in excellent yield and purity.

Alcohols↗
PubMed2002

Capture-ROMP-release: application for the synthesis of O-alkylhydroxylamines.

[reaction: see text] A new capture-ROMP-release method for chromatography-free purification of N-hydroxysuccinimde Mitsunobu reactions is described. The Mitsunobu reaction captures a variety of alcohols onto a norbornenyl N-hydroxysuccinimide monomer. Subjection of the resulting crude reaction mixture to ROM-polymerization generates a polymer that can be precipitated with methanol and filtered from the Mitsunobu byproducts. Treatment of the polymer with hydrazine releases the substrate from the water-soluble polymer, producing a variety of O-alkylhydroxylamines with good purity.

Hydroxylamines↗
PubMed2002

New developments in chemical library synthesis. Norbornenyl tags for use in phase-switching, sequestration, capture-release and soluble support applications.

A new, general chemical library purification platform is reviewed. This platform makes broad use of (oxa)norbornenyl-tagged reactants, reagents, catalysts, sequestration-enabling reagents and scavengers, in combination with Grubbs catalyst-mediated ring-opening metathesis polymerization (ROMP) reactions as an in situ polymerization purification technique. Extensions of this platform involve the use of preformed ROMP supports in synthesis, and polystyrene-supported Grubbs catalysts, which perform in a boomerang fashion.

Animals↗