A mechanistically unusual base induced [1,3]-H-shift in homoallylic ethers
摘要:
Upon treatment with NaH in DMF the homoallylic ethers 1a-g and the amine 1h undergo a rearrangement into the trisubstituted (Epsilon)- olefins 2a-h. Experiments with isotopically labelled forms of 1a and 1b show that the [1,3]-shift is cleanly intramolecular and proceeds predominantly in the suprafacial mode. (C) 1997 Elsevier Science Ltd.
A concise/catalytic approach for the construction of the C14–C28 fragment of eribulin
作者:Sibadatta Senapati、Chepuri V. Ramana
DOI:10.1039/d1ob00661d
日期:——
A simple approach for the synthesis of the C14–C28 fragment of eribulin has been developed by employing a one-pot gold-catalyzed alkynol cyclization/Kishi reduction to construct the 1,5-cis-tetrahydropyran unit and a cross-metathesis/Sharpless asymmetric dihydroxylation–cycloetherification to install the 1,4-trans-tetrahydrofuran ring. Use of easily accessible building blocks, ease of operation and
The C13−C18 fragment 3 of the novel antibioticbranimycin was prepared along two highly stereocontrolled routes. The first one uses a standard Roush crotylation protocol, whereas the second one proceeds via an allenyl silane propargylation with unexpected stereochemical consequences, which are discussed in detail.