4017-57-6Relevant articles and documents
Synthesis of a Mexican bean beetle azamacrolide allomone via a novel lactam to lactone ring expansion
Gribble, Gordon W.,Silva, Richard A.
, p. 2145 - 2148 (1996)
The Mexican bean beetle (Epilachna varivestis) defensive secretion azamacrolide 1 has been synthesized via the novel ring expansion of N-hydroxyethyl lactam 12, which was prepared in seven steps from cyclooctanone (6).
Synthetic Entry to Polyfunctionalized Molecules through the [3+2]-Cycloaddition of Thiocarbonyl Ylides
Habiger, Christoph,Haut, Franz-Lucas,Korber, Johannes Nepomuk,Müller, Thomas,Magauer, Thomas,Mayer, Peter,Speck, Klaus,Wurst, Klaus
supporting information, (2019/09/06)
Here we present a comprehensive study on the [3+2]-cycloaddition of thiocarbonyl ylides with a wide variety of alkenes and alkynes. The obtained dihydro- and tetrahydrothiophene products serve as exceptionally versatile intermediates providing access to thiophenes, dienes, dendralenes, and vic-quarternary carbon centers. The use of high-pressure conditions enables thermally unstable, sterically encumbered or moderately reactive substrates to undergo the cycloaddition under mild conditions, thereby increasing the yield by up to 58percent. In addition, we showcase its utility by the formal syntheses of the pharmaceuticals NGB 4420 and tenilapine.
The profound effect of the ring size in the electrocyclic opening of cyclobutene-fused bicyclic systems
Ralph, Michael J.,Harrowven, David C.,Gaulier, Steven,Ng, Sean,Booker-Milburn, Kevin I.
supporting information, p. 1527 - 1531 (2015/01/30)
Fused cyclobutenes, prepared by the photocycloaddition of propargyl alcohols to cyclic anhydride chromophores, undergo facile thermochemical ring opening to fused γ-lactones. The size of the fused ring profoundly influences the temperature that is required to facilitate the ring opening (from 50°C to 180°C) and the nature of the product that is formed. Our studies provide new insights into the mechanistic course of these reactions and have been extended to facilitate the preparation of lactams fused to medium-sized rings.
Total synthesis, molecular editing and evaluation of a tripyrrolic natural product: The case of "butylcycloheptylprodigiosin"
Fuerstner, Alois,Radkowski, Karin,Peters, Hartwig,Seidel, Guenter,Wirtz, Conny,Mynott, Richard,Lehmann, Christian W.
, p. 1929 - 1945 (2008/02/03)
Conflicting reports are found in the literature on whether the ortho-pyrrolophane derivative 6, which has been named " butylcycloheptylprodigiosin" even though it is a cyclononane derivative, is a natural product or merely a mis-assigned structure. This dispute has now been resolved by an unambiguous total synthesis of this complex alkaloid which confirms the initial structure assignment. The chosen approach is largely catalysis-based, featuring the first application of a "Narasaka-Heck" reaction in natural product chemistry. This palladium-catalyzed transformation allows the unsaturated oxime ester 26 to be converted into the bicyclic dihydropyrrole 27. Other notable reactions of the reported approach to 6 are a regioselective Tsuji-Trost reaction of the doubly allylic acetate 21 with methyl acetoacetate. a base-induced aromatization of 27 to the corresponding pyrrole 28. a chemoselective oxidation of the benzylic methyl group in 33 with cerium ammonium nitrate in a biphasic reaction medium that does not affect the labile pyrrole nucleus, and a Suzuki cross-coupling for the completion of the heterocyclic domain. Diversification in the latter step leads to a set of analogues that differ from the natural product in the terminal (hetero)arene ring. This structural modification results in complete loss of the very pronounced ability of the parent compound 6 to induce oxidative cleavage in double stranded DNA in the presence of Cu11. Several cyclononane-, cyclononene- and cyclononadiene derivatives prepared en route to 6 have been characterized by crystal structure analysis, allowing the conformational behavior of nine-membered carbocycles to be studied.
