573701-31-2Relevant academic research and scientific papers
Nucleophilic Fluorination and Radiofluorination via Aziridinium Intermediates: N-Substituent Influence, Unexpected Regioselectivity, and Differences between Fluorine-19 and Fluorine-18
Médoc, Marie,Sobrio, Franck
, p. 10086 - 10097 (2015/11/03)
The efficient dehydrofluorination and radiofluorination of N,N-disubstituted-β-aminoalcohols through an anchimeric-assisted mechanism was developed. An investigation into the influence of N-substituents on the ring opening of the aziridinium intermediate indicated differences in the isomeric ratio and the yields of fluorinated products obtained from N,N-disubstituted-phenylalaninol. This influence was substantial for 18F-radiofluorination, with yields varying from 0 to 71% at room temperature (RT). Although no significant effects were observed in the fluorine-19 chemistry when the reaction was heated to 90 °C, considerable changes appeared during radiofluorination. In the latter case, the radiochemical yields increased, and degradation of the 2-fluoro-propan-1-amine isomer (b) occurred, leading to a regiospecific reaction in the radiolabeling of [18F]-fluorodeprenyl. This method involving nucleophilic radiofluorination at RT was successfully applied to the radiolabeling of [18F]-2-fluoroethylamines in which the influence of the N-substituent was also observed.
Synthesis of enantiomerically enriched indolines and tetrahydroisoquinolines from (S)-amino acid-derived chiral carbocations: An easy access to (3S,4R)-demethoxy-3-isopropyl diclofensine
Manna, Sudipta Kumar,Panda, Gautam
, p. 8318 - 8324 (2015/01/09)
Enantiomerically enriched indolines and tetrahydroisoquinolines were synthesized within 5 min to 2 h in high yields from easily accessible (S)-amino acid derived chiral carbocations. The diastereoselective Friedel-Crafts reaction is promoted by a Lewis acid (AlCl3) offering trans-diastereoselectivity. The rate of the reaction and diastereoselectivity of the product are significantly influenced by steric hindrance of the amino acids substituents and aryl groups. The methodology can be applied for the synthesis of the enantiomerically enriched bioactive scaffold (3S,4R)-demethoxy-3-isopropyl diclofensine. This journal is
'N-stereogenic quaternary ammonium salts' from L-amino acids: Synthesis, separation, and absolute configuration
Wu, Hua-Fang,Lin, Wen-Bin,Xia, Li-Zi,Luo, Ying-Gang,Chen, Xiao-Zhen,Li, Guo-You,Zhang, Guo-Lin,Pan, Xin-Fu
experimental part, p. 677 - 688 (2009/08/08)
Diastereoisomeric linear and cyclic 'N-chiral quaternary ammonium salts' (QASs) were efficiently synthesized from corresponding L-amino acids in high yields. The diastereoisomers of each pair of 'N-chiral QASs' were successfully separated. The absolute configurations of these QASs were determined predominately by X-ray single-crystal analysis. The 1H-NMR data of 'N-chiral QASs' provided characteristic information on the configuration of the N-chiral center. 'N-Chiral QASs' exemplified by [N(R)]-2a and [N(S)]-2a are stable in protic and aprotic solvents within a broad pH and temperature range.
Stereoselective formation and rearrangement of morpholinium ylides derived from copper carbenoids
Glaeske, Kevin W.,Naidu,West
, p. 917 - 920 (2007/10/03)
Amino diazoacetoacetates 4a-e and 7a,b were prepared from readily available amino alcohols and subjected to copper-catalyzed carbene-transfer reaction. Substrates 4c-e furnished the morpholin-2-ones 5c-e in good yield via the corresponding cyclic ammonium ylides, albeit with poor diastereoselectivity. Substrates 4a,b failed to provide the corresponding morpholinones, perhaps as a result of steric congestion. Cyclic substrates 7a,b underwent conversion to bicyclic morpholinones 8 and 9 in good yield and with moderate to good diastereoselectivity. This result is rationalized via control of the transiently stereogenic ammonium center of the intermediate bicyclic ylides.
