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1.
Chemistry ; 28(71): e202202029, 2022 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-36173921

RESUMO

The first systematic evaluation of the electrostatic potential energy maps of iodonium ylides was conducted. We determined that they possess two σ-holes of differing electron deficiencies, with the more electropositive σ-hole located opposite the dative I-C bond to the ß-dicarbonyl motif, and the lesser electropositive σ-hole located opposite the iodoarene C-I bond. We also conducted the first systematic evaluation of carboxylic acids, phenols and thiophenols in the O/S-alkylation reaction of iodonium ylides. While carboxylic acids and thiophenols were found to be generally viable, only phenols possessing electron-withdrawing substituents were effective. This high-yielding and highly chemoselective reaction is believed to involve halogen-bond activation of heteroatoms, and nicely complements existing diazo-based methods for alkylation of acidic functional groups.

2.
Org Lett ; 22(8): 3140-3144, 2020 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-32242670

RESUMO

The GaCl3-catalyzed [4 + 2] cycloaddition between alkoxy- and aryl-activated donor-acceptor cyclobutane diesters and cis-diazene 1a (4-phenyl-1,2,4-triazoline-3,5-dione, PTAD) is disclosed. The reaction provides hexahydropyridazine derivatives as single diastereomers in good to excellent yields in most cases. The structural assignment of the cycloadduct 3b was unambiguously established by single-crystal X-ray diffraction.

3.
Angew Chem Int Ed Engl ; 58(47): 16959-16965, 2019 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-31486231

RESUMO

A facile and highly chemoselective synthesis of doubly activated cyclopropanes is reported where mixtures of alkenes and ß-dicarbonyl-derived iodonium ylides are irradiated with light from blue LEDs. This metal-free synthesis gives cyclopropanes in yields up to 96 %, is operative with cyclic and acyclic ylides, and proceeds with a variety of electronically-diverse alkenes. Computational analysis explains the high selectivity observed, which derives from exclusive HOMO to LUMO excitation, instead of free carbene generation. The procedure is operationally simple, uses no photocatalyst, and provides access in one step to important building blocks for complex molecule synthesis.

4.
Org Biomol Chem ; 16(44): 8486-8490, 2018 11 14.
Artigo em Inglês | MEDLINE | ID: mdl-30379184

RESUMO

Reacting Wittig reagents and the hypervalent iodine reagent iodosotoluene, in the presence of 10 mol% Cu(tfacac)2 and 5 equiv. of alkene, results in a novel cyclopropanation reaction. The reagent combination is believed to generate a transient monocarbonyl iodonium ylide (MCIY) in situ, which can be intercepted by the copper catalyst to give a metallocarbene. Both ester and ketone derived phosphoranes can be used, as can styrenyl and non-styrenyl alkenes, which provides cyclopropanes in yields up to 81%.

5.
Org Lett ; 18(12): 2922-5, 2016 06 17.
Artigo em Inglês | MEDLINE | ID: mdl-27267360

RESUMO

Tandem ring opening, elimination, and cycloaddition of donor-acceptor cyclopropanes were observed in Yb(OTf)3-catalyzed cycloaddition with nitrosoarenes. The reaction results in formation of tetrahydro-1,2-oxazine instead of the normal cycloadduct isoxazolidine via in situ nitrone formation. A similar cascade sequence was observed with cis-diazines. Mechanistic studies on this unique transformation offer an entirely new approach for reaction design with donor-acceptor cyclopropanes.

6.
J Am Chem Soc ; 131(28): 9622-3, 2009 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-19552408

RESUMO

An entirely carbohydrate-based immunogen consisting of a zwitterionic polysaccharide (ZPS) PS A1 and the well-known tumor antigen Tn has been designed, synthesized, and studied for immunological effects. The PS A1 motif was included to act as an MHCII elicitor for a T-cell-dependent immune response with increased immunogenicity against tumor-associated carbohydrate antigens, providing an alternative to carrier proteins. Through the use of C57BL/6 mice, it has been shown that chemical modification of PS A1 does not alter the recognition sequence responsible for an MHCII-mediated, T-cell-dependent immune response. The Tn-PS A1 conjugate construct confers specificity toward the Tn antigen alone, and specific carbohydrate immunoglobulins, namely, IgG3, are generated from intraperitoneal immunizations with or without adjuvant. The properties of the vaccine candidate are attributed to a site-specific linking strategy that incurs significant incorporation of Tn antigen.


Assuntos
Antígenos Glicosídicos Associados a Tumores/imunologia , Imunoconjugados/imunologia , Oligossacarídeos/imunologia , Vacinas Sintéticas/imunologia , Animais , Antígenos Glicosídicos Associados a Tumores/química , Bovinos , Haptenos/imunologia , Antígenos de Histocompatibilidade/imunologia , Imunoconjugados/química , Imunoterapia , Camundongos , Neoplasias/imunologia , Neoplasias/terapia , Oligossacarídeos/química , Vacinas Sintéticas/química
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