Bogdan Barnych | University of California, Davis (original) (raw)
Papers by Bogdan Barnych
Tetrahedron, 2013
ABSTRACT The first total synthesis of andavadoic acid, a naturally occurring five-membered ring p... more ABSTRACT The first total synthesis of andavadoic acid, a naturally occurring five-membered ring peroxide, and its absolute configuration assignment are reported. Central to this venture was the development of an effective synthesis of a key β-hydroperoxy epoxy ester from (R)-epichlorohydrin via chemoselective methylenation with Nysted reagent in the presence of Ti(Oi-Pr)2Cl2 and chemo- and regioselective Mukaiyama–Isayama peroxidation. This approach also featured the construction of the 1,2-dioxolane ring system by an efficient base-promoted 5-exo epoxide opening by a hydroperoxy group.
Organic Letters, 2012
A first total synthesis of (-)-ent-plakortolide I and seco-plakortolide E was accomplished from (... more A first total synthesis of (-)-ent-plakortolide I and seco-plakortolide E was accomplished from (S)-2-methylglycidol. The relevant key reactions involve a diastereoselective Mukaiyama aldol reaction, a regioselective hydroperoxysilylation, and elaboration of the 1,2-dioxane ring by intramolecular Michael addition of a hydroperoxide group to a butenolide. This synthesis allowed the revision of the absolute configuration of plakortolide I and structural revision of plakortolide E.
Tetrahedron, 2012
ABSTRACT Our efforts in construction the 1,2-dioxane ring of plakortolides through two approaches... more ABSTRACT Our efforts in construction the 1,2-dioxane ring of plakortolides through two approaches are described. The first one involved as a key step an acid catalyzed 6-endo ring closure of b-hydroperoxy trans-epoxides directed by a vinyl group adjacent to the epoxide function. By this route, an advanced intermediate of plakortolides was obtained in six steps and 35% overall yield. The second approach featured a 1,2-dioxane ring forming by a double opening of bis-epoxides by ethereal hydrogen peroxide. This reaction did not proceed in the expected sense and exclusive formation of hydroperoxy tetrahydropyran derivatives was observed via a tandem oxacyclizationehydroperoxidation sequence.
Journal of Natural Products, 2012
The relative configuration of the plakortolide metabolite (4) isolated from a Madagascan Plakorti... more The relative configuration of the plakortolide metabolite (4) isolated from a Madagascan Plakortis sp. and named (+)-plakortolide I is revised following reassignment of the ¹³C signals for C-7 and C-16, thereby establishing that the metabolite isolated was likely (+)-plakortolide E (3). We propose that the name "plakortolide I" should be retained for the plakortolide metabolite 5 first isolated by the Faulkner group; its enantiomer 4 can then be named ent-plakortolide I in line with the description of Barnych and Vatèle. The spectroscopic data for MPA esters prepared from synthetic samples of seco derivatives of plakortolide E (3) and ent-plakortolide I (4) were compared with those of MPA esters of seco derivatives from naturally isolated plakortolides L (1) and K (2) and of seco-plakortolide E (6a). Likewise, the spectroscopic data for MTPA esters derived from 3 and 4 were compared with data for the MTPA esters derived from 5. These various comparisons established that the sign of the specific rotation associated with the natural isolates is an unreliable indicator of absolute configuration and verify that the absolute configurations of plakortolides L (1), K (2), E (3), and I (5) are (3S, 4S, 6S), (3R, 4R, 6S), (3R, 4R, 6R), and (3S, 4S, 6R), respectively.
ChemInform, 2011
ABSTRACT A sequential one-pot synthesis for the oxidation of primary and secondary tert-butyldime... more ABSTRACT A sequential one-pot synthesis for the oxidation of primary and secondary tert-butyldimethylsilyl (TBDMS) ethers, using catalytic amounts of metal triflates and TEMPO in combination with PhIO or PhI(OAc)(2) in THF or acetonitrile, is described. Acid-sensitive protecting groups such as methylidene, isopropylidene, acetals, and Boc are unaffected under the reaction conditions. Another feature of this procedure is its high selectivity for TBDMS ethers over tert-butyldiphenylsilyl ethers and of aliphatic TBDMS groups over phenolic TBDMS groups.
![Research paper thumbnail of Corrigendum to “Exploratory studies toward the synthesis of the peroxylactone unit of plakortolides” [Tetrahedron 68 (2012) 3717–3724]](https://attachments.academia-assets.com/41798840/thumbnails/1.jpg)
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Cheminform, 2007
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Heteroatom Chemistry, 2009
The reaction of β-dialkylaminocrotontriles with phosphorus(III) halides has been investigated. Th... more The reaction of β-dialkylaminocrotontriles with phosphorus(III) halides has been investigated. The basicity of the dialkylamino group influences the phosphorylation markedly, with pyrrolidine being the amine of choice. It was found that a solvent and the ratio of triethylamine play a significant role in phosphorylation. Although chloro- and dichlorophosphine derivatives proved impossible to separate as individual compounds; their solutions can be successfully used for further transformations. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:194–201, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20532
Cheminform, 2009
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Tetrahedron, 2007
A Convenient Approach to λ 5 -Phosphinines via Interaction of Phosphorylated 3-Pyrrolidinocrotoni... more A Convenient Approach to λ 5 -Phosphinines via Interaction of Phosphorylated 3-Pyrrolidinocrotonitrile with 2-Bromoacetophenones. -The method avoids the utilization of sensitive λ 3 -phosphinine intermediates which hampers alternative procedures for preparation of the title compounds. -(SVYASCHENKO, Y. V.; KOSTYUK*, A. N.; BARNYCH, B. B.; VOLOCHNYUK, D. M.; Tetrahedron 63 (2007) 25, 5656-5664; Inst. Org. Chem., Natl. Acad. Sci. Ukr., Kiev 02094, Ukraine; Eng.) -Nuesgen 40-169
Biosensors & Bioelectronics, 2011
Tetrahedron, 2013
ABSTRACT The first total synthesis of andavadoic acid, a naturally occurring five-membered ring p... more ABSTRACT The first total synthesis of andavadoic acid, a naturally occurring five-membered ring peroxide, and its absolute configuration assignment are reported. Central to this venture was the development of an effective synthesis of a key β-hydroperoxy epoxy ester from (R)-epichlorohydrin via chemoselective methylenation with Nysted reagent in the presence of Ti(Oi-Pr)2Cl2 and chemo- and regioselective Mukaiyama–Isayama peroxidation. This approach also featured the construction of the 1,2-dioxolane ring system by an efficient base-promoted 5-exo epoxide opening by a hydroperoxy group.
Organic Letters, 2012
A first total synthesis of (-)-ent-plakortolide I and seco-plakortolide E was accomplished from (... more A first total synthesis of (-)-ent-plakortolide I and seco-plakortolide E was accomplished from (S)-2-methylglycidol. The relevant key reactions involve a diastereoselective Mukaiyama aldol reaction, a regioselective hydroperoxysilylation, and elaboration of the 1,2-dioxane ring by intramolecular Michael addition of a hydroperoxide group to a butenolide. This synthesis allowed the revision of the absolute configuration of plakortolide I and structural revision of plakortolide E.
Tetrahedron, 2012
ABSTRACT Our efforts in construction the 1,2-dioxane ring of plakortolides through two approaches... more ABSTRACT Our efforts in construction the 1,2-dioxane ring of plakortolides through two approaches are described. The first one involved as a key step an acid catalyzed 6-endo ring closure of b-hydroperoxy trans-epoxides directed by a vinyl group adjacent to the epoxide function. By this route, an advanced intermediate of plakortolides was obtained in six steps and 35% overall yield. The second approach featured a 1,2-dioxane ring forming by a double opening of bis-epoxides by ethereal hydrogen peroxide. This reaction did not proceed in the expected sense and exclusive formation of hydroperoxy tetrahydropyran derivatives was observed via a tandem oxacyclizationehydroperoxidation sequence.
Journal of Natural Products, 2012
The relative configuration of the plakortolide metabolite (4) isolated from a Madagascan Plakorti... more The relative configuration of the plakortolide metabolite (4) isolated from a Madagascan Plakortis sp. and named (+)-plakortolide I is revised following reassignment of the ¹³C signals for C-7 and C-16, thereby establishing that the metabolite isolated was likely (+)-plakortolide E (3). We propose that the name "plakortolide I" should be retained for the plakortolide metabolite 5 first isolated by the Faulkner group; its enantiomer 4 can then be named ent-plakortolide I in line with the description of Barnych and Vatèle. The spectroscopic data for MPA esters prepared from synthetic samples of seco derivatives of plakortolide E (3) and ent-plakortolide I (4) were compared with those of MPA esters of seco derivatives from naturally isolated plakortolides L (1) and K (2) and of seco-plakortolide E (6a). Likewise, the spectroscopic data for MTPA esters derived from 3 and 4 were compared with data for the MTPA esters derived from 5. These various comparisons established that the sign of the specific rotation associated with the natural isolates is an unreliable indicator of absolute configuration and verify that the absolute configurations of plakortolides L (1), K (2), E (3), and I (5) are (3S, 4S, 6S), (3R, 4R, 6S), (3R, 4R, 6R), and (3S, 4S, 6R), respectively.
ChemInform, 2011
ABSTRACT A sequential one-pot synthesis for the oxidation of primary and secondary tert-butyldime... more ABSTRACT A sequential one-pot synthesis for the oxidation of primary and secondary tert-butyldimethylsilyl (TBDMS) ethers, using catalytic amounts of metal triflates and TEMPO in combination with PhIO or PhI(OAc)(2) in THF or acetonitrile, is described. Acid-sensitive protecting groups such as methylidene, isopropylidene, acetals, and Boc are unaffected under the reaction conditions. Another feature of this procedure is its high selectivity for TBDMS ethers over tert-butyldiphenylsilyl ethers and of aliphatic TBDMS groups over phenolic TBDMS groups.
Cheminform, 2007
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Heteroatom Chemistry, 2009
The reaction of β-dialkylaminocrotontriles with phosphorus(III) halides has been investigated. Th... more The reaction of β-dialkylaminocrotontriles with phosphorus(III) halides has been investigated. The basicity of the dialkylamino group influences the phosphorylation markedly, with pyrrolidine being the amine of choice. It was found that a solvent and the ratio of triethylamine play a significant role in phosphorylation. Although chloro- and dichlorophosphine derivatives proved impossible to separate as individual compounds; their solutions can be successfully used for further transformations. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:194–201, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20532
Cheminform, 2009
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Tetrahedron, 2007
A Convenient Approach to λ 5 -Phosphinines via Interaction of Phosphorylated 3-Pyrrolidinocrotoni... more A Convenient Approach to λ 5 -Phosphinines via Interaction of Phosphorylated 3-Pyrrolidinocrotonitrile with 2-Bromoacetophenones. -The method avoids the utilization of sensitive λ 3 -phosphinine intermediates which hampers alternative procedures for preparation of the title compounds. -(SVYASCHENKO, Y. V.; KOSTYUK*, A. N.; BARNYCH, B. B.; VOLOCHNYUK, D. M.; Tetrahedron 63 (2007) 25, 5656-5664; Inst. Org. Chem., Natl. Acad. Sci. Ukr., Kiev 02094, Ukraine; Eng.) -Nuesgen 40-169
Biosensors & Bioelectronics, 2011