1.Organocatalytic highly enantioselective nitroaldol reaction of alpha-ketophosphonates and nitromethane.
Mandal T1, Samanta S, Zhao CG. Org Lett. 2007 Mar 1;9(5):943-5. Epub 2007 Feb 7.
[reaction: see text] The first organocatalytic highly enantioselective nitroaldol reaction of alpha-ketophosphonates and nitromethane has been realized by using cupreine (2) or 9-O-benzylcupreine (3) as the catalyst. Both catalysts are highly reactive and highly enantioselective. alpha-Hydroxy-beta-nitrophosphonates have been synthesized in good yields and excellent enantioselectivities (>or=90% ee) at a low catalyst loading (5 mol %). These nitroaldol products may be reduced to the biologically significant beta-amino-alpha-hydroxyphosphonates with complete retention of the stereochemistry.
2.Hydroxyalkylation with cyclic alkylene esters; synthesis of hydroxyethylapocupreine.
CARLSON WW, CRETCHER LH. J Am Chem Soc. 1947 Aug;69(8):1952-6.
3.Bioactive cinchona alkaloids from Remijia peruviana.
Ruiz-Mesia L1, Ruiz-Mesía W, Reina M, Martínez-Diaz R, de Inés C, Guadaño A, González-Coloma A. J Agric Food Chem. 2005 Mar 23;53(6):1921-6.
Three known Cinchona alkaloids of the quinine type, quinine (1), cupreine (2), cinchonine (3), and the possible artifact cinchonine-HCl (3-HCl), along with two new ones, acetylcupreine (4) and N-ethylquinine (5), have been isolated from the bark of Remijia peruviana (Rubiaceae). Their stereochemical structures were established by high resolution NMR spectroscopy. Alkaloids 2-4 had antifeedant effects on Leptinotarsa decemlineata with varying potencies. Compound 4 was cytotoxic to both insect Sf9 and mammalian CHO cells after 48 h of incubation, while 3-HCl had stronger and selective cytotoxicity to Sf9. Quinine 1 had a moderate to low effect on Trypanosoma cruzi. Tumoral cells were also affected by these alkaloids, with 4 and 3-HCl being the most cytotoxic to all the cell lines tested. Overall, the 8R, 9S configurations, as in 3 and 3-HCl, as well as the C-6'acetylated alkaloid 4, with an 8S, 9R configuration, showed stronger biological effects.
4.Synthesis of 2,3,4-Trisubstituted Thiochromanes using an Organocatalytic Enantioselective Tandem Michael-Henry Reaction.
Dodda R1, Goldman JJ, Mandal T, Zhao CG, Broker GA, Tiekink ER. Adv Synth Catal. 2008 Feb 26;350(4):537-541.
Enantioenriched 2,3,4-trisubstituted thiochromanes have been synthesized by using a cupreine-catalyzed tandem Michael addition-Henry reaction between 2-mercaptobenzaldehydes and β-nitrostyrenes. Good diastereoselectivities and enantioselectivities were obtained for the title compounds, which may be further improved through a single recrystallization (up to 98% de and> 99% ee).
