151101-22-3Relevant academic research and scientific papers
Asymmetric synthesis of 4-amino-γ-butyrolactones via lithium amide conjugate addition
Abraham, Elin,Cooke, Jason W.B.,Davies, Stephen G.,Naylor, Alan,Nicholson, Rebecca L.,Price, Paul. D.,Smith, Andrew D.
, p. 5855 - 5872 (2008/02/02)
Upon treatment with homochiral lithium (R)-N-benzyl-N-(α-methylbenzyl)amide, γ-benzyloxy but-2-enoates undergo competitive conjugate addition and γ-deprotonation, while γ-tert-butyldimethylsilyloxy but-2-enoates undergo exclusive conjugate addition. Treatment of γ-benzyloxy or γ-tert-butyldimethylsilyloxy but-2-enamides with lithium (R)-N-benzyl-N-(α-methylbenzyl)amide furnishes exclusively the γ-benzyloxy- or γ-tert-butyldimethylsilyloxy-β-amino amide products of conjugate addition in high de. The γ-tert-butyldimethylsilyloxy-β-amino butanoate products of conjugate addition readily undergo O-desilylation and concomitant cyclisation to furnish 4-[N-benzyl-N-(α-methylbenzyl)amino]-γ-butyrolactone, which may be stereoselectively functionalised via deprotonation and alkylation?to give the corresponding trans-3-alkyl-4-amino-γ-butyrolactones. Alternatively, stereoselective alkylation of γ-benzyloxy- or γ-tert-butyldimethylsilyloxy-β-amino butanoates and butanamides through enolate formation and alkylation following a tandem (via the (Z)-lithium enolate) or stepwise (via the (E)-lithium enolate) protocol gives a range of separable syn- and anti-α-alkyl-β-amino esters and amides. O-Silyl deprotection of the syn- and anti-α-alkyl-β-amino butanoates with TBAF and concomitant cyclisation provide trans-3-alkyl-4-amino-γ-butyrolactones, consistent with epimerisation to the thermodynamically favoured trans-lactone occurring upon deprotection.
Aza-cope rearrangement-Mannich cyclizations for the formation of complex tricyclic amines: Stereocontrolled total synthesis of (±)-gelsemine
Earley, William G.,Jacobsen, Jon E.,Madin, Andrew,Meier, G. Patrick,O'Donnell, Christopher J.,Oh, Taeboem,Old, David W.,Overman, Larry E.,Sharp, Matthew J.
, p. 18046 - 18053 (2007/10/03)
A detailed examination of the use of aza-Cope rearrangement-Mannich cyclization sequences for assembling the azatricyclo[4.4.0.02,8] decane core of gelsemine is described. Iminium ions and N-acyloxyiminium ions derived from endo-oriented 1-methoxy- or 1-hydroxybicyclo[2.2.2]oct-5-enylamines do not undergo the first step of this sequence, cationic aza-Cope rearrangement, to form cis-hydroisoquinolinium ions. However, the analogous base-promoted oxy-aza-Cope rearrangement does take place to form cis-hydroisoquinolones containing functionality that allows iminium ions or N-acyloxyiminium ions to be generated regioselectively in a subsequent step. Mannich cyclization of cis-hydroisoquinolones prepared in this way efficiently assembles the azatricyclo[4.4.0.02,8]decane unit of gelsemine. Using a sequential base-promoted oxy-aza-Cope rearrangement/Mannich cyclization sequence, gram quantities of azatricyclo[4.4.0.02,8]decanone 18, a central intermediate in our total of (±)-gelsemine, were prepared from 3-methylanisole in 12 steps and 16% overall yield.
Biogenetically inspired approach to the Strychnos alkaloids. Concise syntheses of (±)-akuammicine and (±)-strychnine
Ito,Clark,Mortimore,Goh,Martin
, p. 8003 - 8010 (2007/10/03)
A linear synthesis of the indole alkaloid (±)-akuammicine (2) was completed by a novel sequence of reactions requiring only 10 steps from commercially available starting materials. The approach features a tandem vinylogous Mannich addition and an intramol
Syntheses of α,β-unsaturated carbonyl compounds from the reactions of monosubstituted ozonides with stable phosphonium ylides
Hon, Yung-Son,Lu, Ling,Chang, Rong-Chi,Lin, Sheng-Wun,Sun, Pei-Pei,Lee, Chia-Fu
, p. 9269 - 9279 (2007/10/03)
Ozonides derived from terminal alkenes reacted with 1.3 mol equiv. of stable phosphonium ylides to give (E)-αβ-unsaturated carbonyl compounds in good to excellent yields. No reducing agent is needed in the reaction. However, alkoxyalkyl-substituted ozonides afforded a mixture of (Z)- and (E)-αβ-unsaturated carbonyl compounds under similar condition. The E/Z isomeric ratio is affected by the position of the heteroatom in the substituent of the ozonides. The possible mechanism of this reaction will be discussed. (C) 2000 Elsevier Science Ltd.
