A Synthesis of Alsmaphorazine B Demonstrates the Chemical Feasibility of a New Biogenetic Hypothesis
摘要:
An N-oxide fragmentation/hydroxylamine oxidation/intramolecular 1,3-dipolar cycloaddition. Cascade, efficiently converted an oxidized congener of akuammicine into the complex, hexacyclic architecture of the alsmaphorazine alkaloids. This dramatic structural Change shows the chemical feasibility of our novel proposal for alsmaphorazine biogenesis, Critical to these endeavors was a marked improvement in our previously reported Zincke aldehyde cycloaddition approach to indole alkaloids, which permitted the gram--scale synthesis of akuammicine. The chemoselective oxidations of akuammicine leading tip to the key rearrangement also generated several biogenetically related alkaloids of the alstolucine and alpneumine families.
Synthesis of Cyclic Alkenyl Dimethylsiloxanes from Alkynyl Benzyldimethylsilanes and Application in Polyene Synthesis
作者:Haraldur G. Gudmundsson、Christian J. Kuper、Damien Cornut、Felix Urbitsch、Bryony L. Elbert、Edward A. Anderson
DOI:10.1021/acs.joc.9b01664
日期:2019.11.15
Cyclic dimethylalkenylsiloxanes, useful motifs for (Z)-selective Hiyama cross-coupling, are accessed from alkynyl benzyldimethylsilanes featuring adjacent allylic or homoallylic oxygen substituents by semihydrogenation/debenzylation/cyclization. While formation of 5- and 6-membered rings can be achieved from the free alcohols using fluoride or silanolate, allylic acetate precursors to 5-membered rings
Selective Late‐Stage Sulfonyl Chloride Formation from Sulfonamides Enabled by Pyry‐BF
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作者:Alejandro Gómez‐Palomino、Josep Cornella
DOI:10.1002/anie.201910895
日期:2019.12.9
Reported here is a simple and practical functionalization of primary sulfonamides, by means of a pyrylium salt (Pyry-BF4 ), with nucleophiles. This simple reagent activates the poorly nucleophilic NH2 group in a sulfonamide, enabling the formation of one of the best electrophiles in organic synthesis: a sulfonyl chloride. Because of the variety of primary sulfonamides in pharmaceutical contexts, special
Selective Functionalization of Aminoheterocycles by a Pyrylium Salt
作者:Daniel Moser、Yaya Duan、Feng Wang、Yuanhong Ma、Matthew J. O'Neill、Josep Cornella
DOI:10.1002/anie.201806271
日期:2018.8.20
The functionalization of aminoheterocycles by using a pyrylium tetrafluoroborate reagent (Pyry‐BF4) is presented. This reagent efficiently condenses with a great variety of heterocyclic amines and primes the C−N bond for nucleophilic aromatic substitution. More than 60 examples for the formation of C−O, C−N, C−S, or C−SO2R bonds are disclosed herein. In contrast to C−N activation through diazotization
The invention features methods for the preparation of naturally occurring trihydroxy polyunsaturated eicosanoids and their structural analogs. The invention further provides new derivatives of trihydroxy polyunsaturated eicosanoids that can be prepared according to these methods. The invention also provides trihydroxy polyunsaturated eicosanoids and their use in pharmaceutical compositions.
diyne–triene–diyne structure were synthesized and their solid-statepolymerization was investigated for the first time. The monomers could be polymerized by UV irradiation at 254 nm or 365 nm and increase of the absorption in the visible region was observed during polymerization. Since the absorption tail of the photoproducts shifted to longer wavelength than that of the corresponding monomers, the main photoreaction