Asymmetric Trasformation of Symmetrical Epoxides to Allylic Alcohols by Lithium (<i>S</i>)-2-(<i>N</i>,<i>N</i>-Disubstituted aminomethyl)pyrrolidide
作者:Masatoshi Asami
DOI:10.1246/bcsj.63.721
日期:1990.3
Enantioselective deprotonation of symmetrical epoxides was studied by using chiral lithium amide, prepared from (S)-2-(N,N-disubstituted aminomethyl)pyrrolidine and butyllithium. Chiral allylic alcohols were obtained with moderate to high enantiomeric excesses (ee’s) (41–92% ee) from several cyclic and acyclic epoxides employing lithium (S)-2-(1-pyrrolidinylmethyl)pyrrolidide in tetrahydrofuran (THF) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).
Stereoselective Syntheses of Epothilones A and B via Nitrile Oxide Cycloadditions and Related Studies
作者:Jeffrey W. Bode、Erick M. Carreira
DOI:10.1021/jo015791h
日期:2001.9.1
epothilones A and B are described. The routes described make extensive study of nitrileoxide cycloadditions as surrogates for aldoladdition reactions and have led to the realization of a highly convergent synthesis based on the Kanemasa hydroxyl-directed nitrileoxide cycloaddition. As well, our synthetic efforts have led to the development of new reaction methodologies and served as the proving ground for
Tandem Allylboration-Prins Reaction for the Rapid Construction of Substituted Tetrahydropyrans: Application to the Total Synthesis of (−)-Clavosolide A
作者:Alba Millán、James R. Smith、Jack L.-Y. Chen、Varinder K. Aggarwal
DOI:10.1002/anie.201511140
日期:2016.2.12
Tetrahydropyrans are common motifs in natural products and have now been constructed with high stereocontrol through a three-component allylboration-Prins reaction sequence. This methodology has been applied to a concise (13 steps) and efficient (14 % overall yield) synthesis of the macrolide (-)-clavosolide A. The synthesis also features an early stage glycosidation reaction to introduce the xylose
Vinyl glycosides in oligosaccharide synthesis (part 4): glycosidase-catalysed preparation of substituted allyl glycosides
作者:Robin R. Gibson、Roger P. Dickinson、Geert-Jan Boons
DOI:10.1039/a704703g
日期:——
But-3-en-2-yl glycosides have been obtained by glycosidase-catalysed transformations under thermodynamic conditions, and reaction parameters have been optimised. It has been shown that the enzymes can be immobilised on non-ionic Amberlite resin (XAD-4) and can conveniently be retrieved and re-used in a subsequent glycosylation. The enzyme-catalysed reactions display some diastereodifferentiation with a preference for the (R)- over the (S)-alcohol. An increase in size of the aliphatic substituent on the allyl alcohol gives a significant improvement of diastereoselection.