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Janick Ardisson - One of the best experts on this subject based on the ideXlab platform.
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Relative Stereochemical Determination and Synthesis of the C17–C25 δ‑Lactone Fragment of Hemicalide
2016Co-Authors: Etienne Fleury, Ange Pancrazi, Geoffroy Sorin, Elise Prost, François Sautel, Georges Massiot, Marie-isabelle Lannou, Janick ArdissonAbstract:Hemicalide is a novel marine metabolite polyketide distinguished by a unique mechanism of action. Because of insufficient quantities of purified material, this natural product has evaded complete stereochemical assignments. Recently, we have determined the relative stereochemistry of the C8–C13 hexad by synthesizing the C1–C13 fragment. Presently, we report the assignment of the C17–C25 δ-lactone fragment. NMR analysis of authentic hemicalide along with a computational conformation study allowed us to reduce the number of putative relative isomers from 16 to 4. Concise syntheses of the four candidate diastereomers were achieved using a common strategy based on a Dias Aldehyde Allylation reaction, an intramolecular Horner–Wadsworth–Emmons olefination, and a dihydroxylation reaction. Finally, thorough NMR comparisons enabled us to deduce the relative stereochemistry of the C1–C17 fragment with high certainty
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secondary allyltitanium iv reagents in Aldehyde Allylation i extension of the hoppe reaction to γ alkoxy secondary allyl carbamates
Synthesis, 2004Co-Authors: Patrick Razon, Sylvie Dhulut, Sophie Bezzeninelafollee, Jacques Courtieu, Ange Pancrazi, Janick ArdissonAbstract:An efficient access to optically active (R)- or (S)-γ-alkoxy allyltitanium(IV) intermediates, in Aldehyde Allylation reactions, is described. Enantiomeric γ-alkoxy secondary allyl carbamates (R)- and (S)-14 were first prepared. Determination of their enantiomeric excess was realised on the corresponding deuterated isotopic derivatives by NMR in chiral liquid media. Subsequent Aldehyde Allylation reaction with propanal performed under Hoppe n-BuLi.(-)-sparteine/Ti(Oi-Pr) 4 or n-BuLi.TMEDA/Ti(Oi-Pr) 4 conditions, led to both enantiomeric homoallylic alcohols 15 or ent-15 in 90% yield, 100% ed and 80% ee.
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primary and secondary allyltitanium iv reagents in Aldehyde Allylation ii application to an enantioselective preparation of a c1 c7 fragment of spiramycin
Synthesis, 2004Co-Authors: Patrick Razon, Sylvie Dhulut, Sophie Bezzeninelafollee, Ange Pancrazi, Marieange Nzoutani, Janick ArdissonAbstract:A synthetic approach to the eastern part of spiramycin, an important antibiotic compound, is described. Introduction of the side chain was first envisaged through a Hoppe Aldehyde Allylation. This reaction was carried outbetween an optically pure Aldehyde 32 and a (′)-γ-alkoxy allyltitanium(IV) species derived from a primary γ-alkoxy allyl (diisopropyl)carbamate. Under kinetic resolution conditions, the anti-Cram compound 35 was obtained in an 80:20 mixture, with the Cram isomer 34, in 81% yield. Employing the optically pure (S)-γ-alkoxy allyl (diisopropyl)carbamate 36, the corresponding (R)-γ-alkoxy allyltitanium (R)-'Ti'-III was generated under n-BuLi.TMEDA/Ti(Oi-Pr) 4 conditions, that reacted with Aldehyde 32 in double stereodifferentiation to deliver the expected Cram compound 40 in 80% yield (95% de). This latter corresponded to the C1-C7 fragment of spiramycin.
Patrick Razon - One of the best experts on this subject based on the ideXlab platform.
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secondary allyltitanium iv reagents in Aldehyde Allylation i extension of the hoppe reaction to γ alkoxy secondary allyl carbamates
Synthesis, 2004Co-Authors: Patrick Razon, Sylvie Dhulut, Sophie Bezzeninelafollee, Jacques Courtieu, Ange Pancrazi, Janick ArdissonAbstract:An efficient access to optically active (R)- or (S)-γ-alkoxy allyltitanium(IV) intermediates, in Aldehyde Allylation reactions, is described. Enantiomeric γ-alkoxy secondary allyl carbamates (R)- and (S)-14 were first prepared. Determination of their enantiomeric excess was realised on the corresponding deuterated isotopic derivatives by NMR in chiral liquid media. Subsequent Aldehyde Allylation reaction with propanal performed under Hoppe n-BuLi.(-)-sparteine/Ti(Oi-Pr) 4 or n-BuLi.TMEDA/Ti(Oi-Pr) 4 conditions, led to both enantiomeric homoallylic alcohols 15 or ent-15 in 90% yield, 100% ed and 80% ee.
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primary and secondary allyltitanium iv reagents in Aldehyde Allylation ii application to an enantioselective preparation of a c1 c7 fragment of spiramycin
Synthesis, 2004Co-Authors: Patrick Razon, Sylvie Dhulut, Sophie Bezzeninelafollee, Ange Pancrazi, Marieange Nzoutani, Janick ArdissonAbstract:A synthetic approach to the eastern part of spiramycin, an important antibiotic compound, is described. Introduction of the side chain was first envisaged through a Hoppe Aldehyde Allylation. This reaction was carried outbetween an optically pure Aldehyde 32 and a (′)-γ-alkoxy allyltitanium(IV) species derived from a primary γ-alkoxy allyl (diisopropyl)carbamate. Under kinetic resolution conditions, the anti-Cram compound 35 was obtained in an 80:20 mixture, with the Cram isomer 34, in 81% yield. Employing the optically pure (S)-γ-alkoxy allyl (diisopropyl)carbamate 36, the corresponding (R)-γ-alkoxy allyltitanium (R)-'Ti'-III was generated under n-BuLi.TMEDA/Ti(Oi-Pr) 4 conditions, that reacted with Aldehyde 32 in double stereodifferentiation to deliver the expected Cram compound 40 in 80% yield (95% de). This latter corresponded to the C1-C7 fragment of spiramycin.
Chaojun Li - One of the best experts on this subject based on the ideXlab platform.
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a novel palladium catalyzed coupling of epoxides with allyl bromide mediated by indium i chloride a cascade epoxide rearrangement carbonyl Allylation
Chemical Communications, 2003Co-Authors: Nan Jiang, Qingyuan Hu, Carrolyn S Reid, Yunfeng Lu, Chaojun LiAbstract:A cascade epoxide rearrangement–Aldehyde Allylation was developed by using a combination of InCl and reusable heterogeneous mesoporous silica supported palladium catalysts.
Sophie Bezzeninelafollee - One of the best experts on this subject based on the ideXlab platform.
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secondary allyltitanium iv reagents in Aldehyde Allylation i extension of the hoppe reaction to γ alkoxy secondary allyl carbamates
Synthesis, 2004Co-Authors: Patrick Razon, Sylvie Dhulut, Sophie Bezzeninelafollee, Jacques Courtieu, Ange Pancrazi, Janick ArdissonAbstract:An efficient access to optically active (R)- or (S)-γ-alkoxy allyltitanium(IV) intermediates, in Aldehyde Allylation reactions, is described. Enantiomeric γ-alkoxy secondary allyl carbamates (R)- and (S)-14 were first prepared. Determination of their enantiomeric excess was realised on the corresponding deuterated isotopic derivatives by NMR in chiral liquid media. Subsequent Aldehyde Allylation reaction with propanal performed under Hoppe n-BuLi.(-)-sparteine/Ti(Oi-Pr) 4 or n-BuLi.TMEDA/Ti(Oi-Pr) 4 conditions, led to both enantiomeric homoallylic alcohols 15 or ent-15 in 90% yield, 100% ed and 80% ee.
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primary and secondary allyltitanium iv reagents in Aldehyde Allylation ii application to an enantioselective preparation of a c1 c7 fragment of spiramycin
Synthesis, 2004Co-Authors: Patrick Razon, Sylvie Dhulut, Sophie Bezzeninelafollee, Ange Pancrazi, Marieange Nzoutani, Janick ArdissonAbstract:A synthetic approach to the eastern part of spiramycin, an important antibiotic compound, is described. Introduction of the side chain was first envisaged through a Hoppe Aldehyde Allylation. This reaction was carried outbetween an optically pure Aldehyde 32 and a (′)-γ-alkoxy allyltitanium(IV) species derived from a primary γ-alkoxy allyl (diisopropyl)carbamate. Under kinetic resolution conditions, the anti-Cram compound 35 was obtained in an 80:20 mixture, with the Cram isomer 34, in 81% yield. Employing the optically pure (S)-γ-alkoxy allyl (diisopropyl)carbamate 36, the corresponding (R)-γ-alkoxy allyltitanium (R)-'Ti'-III was generated under n-BuLi.TMEDA/Ti(Oi-Pr) 4 conditions, that reacted with Aldehyde 32 in double stereodifferentiation to deliver the expected Cram compound 40 in 80% yield (95% de). This latter corresponded to the C1-C7 fragment of spiramycin.
Sylvie Dhulut - One of the best experts on this subject based on the ideXlab platform.
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secondary allyltitanium iv reagents in Aldehyde Allylation i extension of the hoppe reaction to γ alkoxy secondary allyl carbamates
Synthesis, 2004Co-Authors: Patrick Razon, Sylvie Dhulut, Sophie Bezzeninelafollee, Jacques Courtieu, Ange Pancrazi, Janick ArdissonAbstract:An efficient access to optically active (R)- or (S)-γ-alkoxy allyltitanium(IV) intermediates, in Aldehyde Allylation reactions, is described. Enantiomeric γ-alkoxy secondary allyl carbamates (R)- and (S)-14 were first prepared. Determination of their enantiomeric excess was realised on the corresponding deuterated isotopic derivatives by NMR in chiral liquid media. Subsequent Aldehyde Allylation reaction with propanal performed under Hoppe n-BuLi.(-)-sparteine/Ti(Oi-Pr) 4 or n-BuLi.TMEDA/Ti(Oi-Pr) 4 conditions, led to both enantiomeric homoallylic alcohols 15 or ent-15 in 90% yield, 100% ed and 80% ee.
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primary and secondary allyltitanium iv reagents in Aldehyde Allylation ii application to an enantioselective preparation of a c1 c7 fragment of spiramycin
Synthesis, 2004Co-Authors: Patrick Razon, Sylvie Dhulut, Sophie Bezzeninelafollee, Ange Pancrazi, Marieange Nzoutani, Janick ArdissonAbstract:A synthetic approach to the eastern part of spiramycin, an important antibiotic compound, is described. Introduction of the side chain was first envisaged through a Hoppe Aldehyde Allylation. This reaction was carried outbetween an optically pure Aldehyde 32 and a (′)-γ-alkoxy allyltitanium(IV) species derived from a primary γ-alkoxy allyl (diisopropyl)carbamate. Under kinetic resolution conditions, the anti-Cram compound 35 was obtained in an 80:20 mixture, with the Cram isomer 34, in 81% yield. Employing the optically pure (S)-γ-alkoxy allyl (diisopropyl)carbamate 36, the corresponding (R)-γ-alkoxy allyltitanium (R)-'Ti'-III was generated under n-BuLi.TMEDA/Ti(Oi-Pr) 4 conditions, that reacted with Aldehyde 32 in double stereodifferentiation to deliver the expected Cram compound 40 in 80% yield (95% de). This latter corresponded to the C1-C7 fragment of spiramycin.