Thiourea-Catalyzed Enantioselective Addition of Indoles to Pyrones: Alkaloid Cores with Quaternary Carbons
摘要:
We report the development of a catalytic method for the enantioselective addition of indoles to pyrone-derived electrophiles. Arylpyrrolidino-derived thioureas catalyze the addition with high stereoselectivity in the presence of catalytic quantities of an achiral Bronsted acid. The indole-pyrone adducts feature a quaternary stereocenter and represent an unusual class of indolines bearing structural resemblance to the hybrid natural product pleiocarpamine.
Studies on the Regioselectivity of Horner-Wadsworth-Emmons (Hwe) Reactions on 3,4-Enuloses. Further Evidence of Phosphonate-Phosphate Rearrangements Through Five Membered Cyclic Intermediates.
作者:Oscar M. Moradei、Cecile M. du Mortier、Alicia Fernández Cirelli
DOI:10.1080/07328309908544032
日期:1999.1
study regio- and stereochemical aspects of the reaction. In the presence of lithium ions, no reaction took place. When sodium enolates were employed, 1,2-addition was the main reaction in chelating solvents, whereas the 1,4-adduct is favoured in the less polar, non chelating toluene. Only 1,2-addition was observed with potassium enolates. Evidence of phosphonate-phosphate rearrangements through five membered
Anomalous Horner-Wadsworth-Emmons reactions on 3,4-enuloses
作者:Oscar M. Moradei、Cecile M. du Mortier、Alicia Fernández Cirelli
DOI:10.1016/s0040-4020(97)00425-0
日期:1997.6
Pyranosic enuloses were subjected to Horner-Wadsworth-Emmons (HWE) conditions using the enolate of dimethyl(methoxycarbonyl)methyl phosphonate and its ethyl analogue. 3-O-Phosphorylation of the products as well as an unusual stereoespecificity were observed. A mechanism involving a phosphonate-phosphate like rearrangement through a five member intermediate followed by benzoate elimination is proposed
TRONCHET, JEAN M. J.;BIZZOZERO, NICOLETTA;BERNARDINELLI, GERALD;GEOFFROY,+, CARBOHYDR. RES., 200,(1990) C. 469-474
作者:TRONCHET, JEAN M. J.、BIZZOZERO, NICOLETTA、BERNARDINELLI, GERALD、GEOFFROY,+
DOI:——
日期:——
3- and 4-Uloses Derived from N-Acetyl-D-glucosamine: A Unique Pair of Complementary Organocatalysts for Asymmetric Epoxidation of Alkenes
作者:Christof Schöberl、Volker Jäger
DOI:10.1002/adsc.201100735
日期:2012.3.16
The 4‐ulose and the 3‐ulose, both derived in two steps from the α‐methyl glycoside of N‐acetyl‐D‐glucosamine (GlcNAc), act as organocatalysts in the asymmetricepoxidation of alkenes, with unprecedented complementary enantioselectivity. The best results are found with α,β‐unsaturated esters as substrates, with enantiomeric ratios up to 90:10 and 11:89, respectively.