Synthesis of the C18-C27 fragment of georatusin

Abstract

Anti-configured 1,3-dimethyl deoxypropionate motifs are important sub-structures in natural products. We describe a bidirectional approach for the rapid construction of highly reduced polyketide fragments for the synthesis of georatusin employing our mono-Zweifel protocol.

The Total Synthesis of Chondrochloren A

“…[11] We believe that this is due to subsequent isomerization as we observe varying amounts of the isomers on different reaction times and in samples of the authentic material. Finally, the synthesis of chondrochloren A (1) (23 linear steps from ribonolactone (17), 0.8 % yield) was enabled by a global TBS-deprotection with HF•NEt 3 .…”

“…Hoppe already reported selected examples in which a diastereoselective Angewandte Chemie Communications metallate rearrangement was observed even in the absence of sparteine. [16] To further explore this transformation as an alternative to the Nozaki-Hiyama-Kishi reaction TIB ester 28 [17] was subjected to 1,2-metallate rearrangements and different conditions with vinylboronic acid pinacol ester 29. Gratifyingly, both enantiomers of sparteine accomplished a stereoselective metallate rearrangement and the corresponding allylic alcohols 30 and epi-30 were obtained as single isomers (Scheme 6).…”

The Total Synthesis of Chondrochloren A

“…Zuschriften 7016 www.angewandte.de metallate rearrangement was observed even in the absence of sparteine. [16] To further explore this transformation as an alternative to the Nozaki-Hiyama-Kishi reaction TIB ester 28 [17] was subjected to 1,2-metallate rearrangements and different conditions with vinylboronic acid pinacol ester 29. Gratifyingly, both enantiomers of sparteine accomplished a stereoselective metallate rearrangement and the corresponding allylic alcohols 30 and epi-30 were obtained as single isomers (Scheme 6).…”

1,2-Metallate Rearrangement as a Toolbox for the Synthesis of Allylic Alcohols

“…4 Recently, we got mechanistic insights for reasoning of the reagent and substrate control observed for the first time in the chondrochloren A (6) synthesis, making this disconnection approach even more useful (Scheme 1d). 6 In order to gain more insights, the tolerance to different functional groups and thus the broad applicability of this new protocol were investigated. Therefore, we have transformed different vinyl boronic esters to the corresponding allylic alcohols (Scheme 1e).…”