ChemInform Abstract: Cycloadditions of 6H‐1,3,4‐Oxadiazin‐6‐ones (4,5‐Diaza‐α‐pyrones) . Part 12. Dieckmann Condensations without Bases.

Christl, Manfred; Lanzendoerfer, U.; Groetsch, M. M.; Hegmann, Joachim; Ditterich, E.; Huettner, G.; Peters, E.‐M.; Peters, Karl; Schnering, H. G. Von

doi:10.1002/chin.199328103

Cited by 4 publications

(4 citation statements)

References 1 publication

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“…Treatment of 7 with 1,1-carbonyldiimidazole (CDI) afforded urea 8 (97%), which was reacted with methyl oxalyl hydrazide 9 20 to provide 10. Dehydration of 10 by treatment of TsCl and Et 3 N afforded the oxadiazole 5 (81% for 2-steps).…”

Section: Resultsmentioning

confidence: 99%

Total Synthesis of (+)-Fendleridine (Aspidoalbidine) and (+)-1-Acetylaspidoalbidine

et al. 2010

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A total synthesis of the Aspidosperma alkaloids (+)-fendleridine (1) and (+)-1-acetylaspidoalbidine (2) is detailed, providing access to both enantiomers of the natural products and establishing their absolute configuration. Central to the synthetic approach is a powerful intramolecular [4 + 2]/[3 + 2] cycloaddition cascade of a 1,3,4-oxadiazole in which the pentacyclic skeleton and all the stereochemistry of the natural products are assembled in a reaction that forms three rings, four C-C bonds, five stereogenic centers including three contiguous quaternary centers, and introduces the correct oxidation state at C19 in a single synthetic operation. The final tetrahydrofuran bridge is subsequently installed in one-step, enlisting an intramolecular alcohol addition to an iminium ion generated by nitrogen assisted opening of the cycloadduct oxido bridge, with a modification that permits release of useful functionality (a ketone) at the cleavage termini.

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Section: Resultsmentioning

confidence: 99%

Total Synthesis of (+)-Fendleridine (Aspidoalbidine) and (+)-1-Acetylaspidoalbidine

et al. 2010

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“…130 The 1,3,4-oxadiazole 218 bearing the tethered indole dipolarophile was prepared from 1-benzyltryptamine 152 (Scheme 65) in a three-step sequence. Treatment of urea 216 with methyl oxalyl hydrazide 215 153 provided 217. Dehydration of 217 on treatment with TsCl and TEA afforded the oxadiazole 218 (81% for two steps).…”

Section: Synthesis Of Five-membered Rings With Two Heteroatomsmentioning

confidence: 99%

Acid Hydrazides, Potent Reagents for Synthesis of Oxygen-, Nitrogen-, and/or Sulfur-Containing Heterocyclic Rings

et al. 2014

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“…Wittig olefination with Ph 3 P=CHOBn18 provided a 1:1 mixture of the separable ( E ) and ( Z ) enol ethers 12 , which were independently carried through the subsequent 3–4 steps for oxadiazole formation and the preparation of ( E )- and ( Z )- 15 . Thus, their Teoc deprotection (Bu 4 NF) and treatment of the crude amines with carbonyldiimidazole afforded ( Z )- and ( E )- 13 (86–100%) that were converted to the oxadiazole precursors 14 by treatment with methyl oxalylhydrazide19 in the presence of HOAc. Cyclization to form the corresponding oxadiazoles 15 was mediated by TsCl and Et 3 N (CH 2 Cl 2 , 94–97%).…”

Section: Resultsmentioning

confidence: 99%

Asymmetric Total Synthesis of Vindorosine, Vindoline, and Key Vinblastine Analogues

2010

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Concise asymmetric total syntheses of vindoline (1) and vindorosine (2) are detailed based on a unique intramolecular [4+2]/[3+2] cycloaddition cascade of 1,3,4-oxadiazoles inspired by the natural product structures. A chiral substituent on the tether linking the dienophile and oxadiazole was used to control the facial selectivity of the initiating Diels-Alder reaction and set the absolute stereochemistry of the remaining six stereocenters in the cascade cycloadduct. This key reaction introduced three rings and four C-C bonds central to the pentacyclic ring system setting all six stereocenters and introducing essentially all the functionality found in the natural products in a single step. Implementation of the approach for the synthesis of 1 and 2 required the development of a ring expansion reaction to provide a 6-membered ring suitably functionalized for introduction of the Δ 6,7 -double bond found in the core structure of the natural products. Two unique approaches were developed that defined our use of a protected hydroxymethyl group as the substituent that controls the stereochemical course of the cycloaddition cascade. In the course of these studies, several analogues of vindoline were prepared containing deep-seated structural changes presently accessible only by total synthesis. These analogues, bearing key modifications at C6-C8, were incorporated into vinblastine analogues and used to probe the unusual importance (100-fold) and define the potential role of the vinblastine Δ 6,7 -double bond.

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ChemInform Abstract: Cycloadditions of 6H‐1,3,4‐Oxadiazin‐6‐ones (4,5‐Diaza‐α‐pyrones) . Part 12. Dieckmann Condensations without Bases.

Cited by 4 publications

References 1 publication

Total Synthesis of (+)-Fendleridine (Aspidoalbidine) and (+)-1-Acetylaspidoalbidine

Total Synthesis of (+)-Fendleridine (Aspidoalbidine) and (+)-1-Acetylaspidoalbidine

Acid Hydrazides, Potent Reagents for Synthesis of Oxygen-, Nitrogen-, and/or Sulfur-Containing Heterocyclic Rings

Asymmetric Total Synthesis of Vindorosine, Vindoline, and Key Vinblastine Analogues

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