Stereoselective Formal Total Synthesis of (-)-Didemniserinolipid B
作者:Kavirayani Prasad、Vasudeva Gandi
DOI:10.1055/s-0029-1217976
日期:2009.10
A formaltotalsynthesis of (-)-didemniserinolipid B from L-(+)-tartaric acid is presented. Key features of the synthesis include construction of the bicyclic acetal core from bisdimethyl amide of tartaric acid and further elaboration by cross metathesis.
Cyclopropylamines from N,N-Dialkylcarboxamides and Grignard Reagents in the Presence of Titanium Tetraisopropoxide or Methyltitanium Triisopropoxide
作者:Armin de Meijere、Vladimir Chaplinski、Harald Winsel、Markus Kordes、Björn Stecker、Vesta Gazizova、Andrei I. Savchenko、Roland Boese、Farina Schill née Brackmann
DOI:10.1002/chem.201001550
日期:2010.12.10
Thirty‐three different N,N‐dialkyl‐ and N‐alkyl‐N‐phosphorylalkyl‐substituted carboxamides 9–17 were treated with unsubstituted as well as with 2‐alkyl‐, 2,2‐dialkyl‐, and 3‐alkenyl‐substituted ethylmagnesium bromides 6 in the presence of stoichiometric amounts of titanium tetraisopropoxide or methyltitanium triisopropoxide to furnish substitutedcyclopropylamines 20–25 in 20–98 % yield, depending
Enantiopure <i>N</i>-Acyldihydropyridones as Synthetic Intermediates: Asymmetric Syntheses of Indolizidine Alkaloids (−)-205A, (−)-207A, and (−)-235B
作者:Daniel L. Comins、Donald H. LaMunyon、Xinghai Chen
DOI:10.1021/jo971448u
日期:1997.11.1
addition of 4-(benzyloxy)butylmagnesium bromide, and vinyl triflate formation provided 13 in a stereoselective fashion. Catalytic reduction of the vinyl triflate moiety, simultaneous cleavage of the benzyl ether and Cbz groups, and cyclization to give amino alcohol 14 was effected via a one-pot reaction. Oxidation of 14 with the Dess-Martin reagent gave a 97% yield of amino aldehyde 4. Synthesis of each
A Versatile Route to 2-Substituted Cyclic 1,3-Dienes via a Copper(I)-Catalyzed Cross-Coupling Reaction of Dienyl Triflates with Grignard Reagents
作者:A. Sofia E. Karlström、Magnus Rönn、Atli Thorarensen、Jan-E. Bäckvall
DOI:10.1021/jo971737i
日期:1998.4.1
A general synthesis of 2-substituted cyclic1,3-dienes in two steps from alpha,beta-unsaturated ketones has been developed. Formation of a dien-2-yl triflate followed by a copper(I)-catalyzed cross-coupling reaction with a Grignard reagent gives 2-substituted dienes in fair to excellent yields. Alkyl, aryl, and allyl Grignard reagents can be used.
Our recently reported titanium-mediated transformation of N,N-dialkylcarboxamides to cyclopropylamines has been applied to N,N-dibenzyl-2-benzyloxyacetamide using a variety of alkylmagnesium bromides to yield 1-(benzyloxymethyl)-1-(dibenzylamino)cyclopropane (15a, 48%) and 2-substitutedanalogs 15b−f (33−48%). These have been transformed in just a few steps into N-Boc-protected methyl esters of 1-