Differentiation of enantiotopic carbonyl groups by the horner-wadsworth-emmons reaction

Molecular Modeling, Total Synthesis, and Biological Evaluations of C9‐Deoxy Bryostatin 1

“…[21] Yamaguchi macrolactonization of the seco acid then afforded the macrolactone in good yield. [22] With the macrolactone in hand, an asymmetric Horner-Wadsworth-Emmons reaction was carried out using the reagent 8 [20] to give a 4:1 mixture of Z/E olefin isomers, which were separated by preparative thin layer chromatography.…”

Total Synthesis of Bryostatin 1: A Short Route

“…It was then subjected to Fuji olefination (4:1 selectivity), [14] before being selectively Odeacetylated at O20, O-acylated, and globally deprotected with LiBF 4 to give bryostatin 1 by a very short route (60 steps overall; longest linear sequence of 31 steps). Although Kecks total synthesis of bryostatin 1 did capitalize on much previous art [2] that had been developed for the fabrication of these molecules, such as Evans Fuji asymmetric olefination [4,14] for control of the bryostatin Bring olefin geometry, Wenders chemoselective oxidative cleavage of a B-ring exocyclic methylene group in the presence of other alkenes to obtain a ketone at C13, [12b] and Wenders C-ring olefination tactics, [12a] it also applied many new concepts that Kecks team had independently conceived. In this respect, Kecks synthetic strategy for assembly of the bryostatin ABC-ring system considerably expanded the scope of a new B-ring construction method that had been pioneered in his laboratory for the synthesis of simplified bryostatin analogues; [15] namely, the intermolecular Prins pyran ringannulation of aldehydes with b-hydroxyalkyl allylsilanes.…”

Totalsynthese von Bryostatin 1: eine kurze Route

“…[7] Einer der jüngsten Hçhepunkte war im Jahr 2010 die kurze asymmetrische Totalsynthese von Bryostatin 1 durch Keck und Mitarbeiter, [8] die zudem im Verlauf der Synthese viele eigens entwickelte Synthesetechniken zum Einsatz brachten und außerdem auf neuartige Methoden der Arbeitsgruppe Rainier zurückgriffen. [9] Die erste Etappe in Kecks Totalsynthese von Bryostatin 1 war die Herstellung des A-Rings in Form des Allylsilans 13 (Schema 1), das in einer neuartigen Lewis-Säure-vermittelten intermolekularen Prins-Reaktion bei niedrigen Temperaturen mit dem "südlichen" Enal 29 (Schema 2) verknüpft werden sollte (Schema 3).[10] Die Synthese von 13 begann mit einer katalytischen asymmetrischen Allylstannierung des Aldehyds 1 in Gegenwart eines aus (S)-binol und Titantetraisopropoxid erzeugten Katalysatorkomplexes (Schema 1).[ [14] und anschließend selektiv an O20 desacetyliert und acyliert. Nach Entfernen sämtlicher Schutzgruppen mit LiBF 4…”