Synthese von Polyin‐Naturstoffen

Abstract

In den vergangenen fünfzig Jahren wurden Hunderte von Polyinen aus natürlichen Proben isoliert. Diese oftmals unbeständigen Verbindungen finden sich gleichsam in alltäglichen Quellen wie Gartengemüse und weniger geläufigen Quellen wie Bakterienkulturen. Die Strukturen von natürlichen Polyinen unterscheiden sich sehr stark, und entsprechend vielfältig sind die biologischen Eigenschaften dieser Naturstoffe. Frühe Syntheseansätze nutzten zum Aufbau des Polyin‐Gerüsts vorzugsweise die kupferkatalysierte oxidative Homo‐ und Heterokupplung von Alkinen. Eine Renaissance der Polyin‐Naturstoffsynthese hat in den vergangenen 25 Jahren jedoch innovative Synthesetechniken hervorgebracht: Übergangsmetallkatalysierte Alkinylierungen und asymmetrische Umwandlungen haben das Repertoire der Polyin‐Naturstoffsynthese merklich erweitert. Der Aufsatz stellt diese Verbesserungen vor und geht auf die natürliche(n) Quelle(n) und die biologische Bedeutung vieler Substanzen ein.

Expanding the Scope of Arylsulfonylacetylenes as Alkynylating Reagents and Mechanistic Insights in the Formation of Csp2Csp and Csp3Csp Bonds from Organolithiums

“…[24] Our method could be also applied to the synthesis of enynes, which are commonly found in naturally occurring compounds. [25] Alkenyllithium 2 I, easily obtained from (E)-1-iodo-1-octene, underwent reactions with 1 a and 1 b to provide 4 aI and 4 bI, respectively, in quantitative yields and with complete retention of the E configuration of the double bond (Scheme 3, a). [26] Analogously, enyne 4 aK, with Z configuration at the double bond (Scheme 3, b), was the only product observed in the reaction of the Li derivative of (Z)-1-bromo-1-propene (2 K) with 1 a.…”

Tris(biphenyl‐4‐yl)silyl‐Endcapped Polyynes

“…[1,2] Furthermore, there are many naturally occurring polyynes that have been isolated, and these compounds often show interesting biological activity. [3] Polyynes are, therefore, desirable synthetic targets, and a number of methods have been reported for their formation. [4] The synthesis of polyynes can be plagued, however, by decrease of stability as a function of polyyne length, and this often leads to decomposition of the polyyne resulting from indiscriminate intermolecular reactions (polymerization).…”

Improved Palladium‐Catalyzed Sonogashira Coupling Reactions of Aryl Chlorides

“…5, [5] 6, [6] 7 [7] ), even though the arylene-ethynylene structure itself does not often occur in natural products, which is in marked contrast to the corresponding vinylene-ethynylene motif. [8] However, the alkynylation of aromatic halides and subsequent cyclization is a widely used method for the synthesis of carbo- [9] and heterocycles [10] as well as intermediates of natural products. [11] It is undeniable that the most effective way to form aryl-alkyne bonds is still palladium-catalyzed coupling reactions of aromatic halides with alkynes in the presence of base and copper co-catalysts.…”