Development of Bifunctional Thiourea Organocatalysts Derived from a Chloramphenicol Base Scaffold and their Use in the Enantioselective Alcoholysis of<i>meso</i>Cyclic Anhydrides
chloramphenicol‐base‐derived thiourea organocatalysts, (1S,2R)‐12 a–f and (1R,2R)‐15 a–c, and their use in the enantioselectivealcoholysis of meso‐anhydrides are described. In particular, hemiesters afforded excellent enantioselectivities if low loadings of (1S,2R)‐12 a–f were used. Almost no enantioselectivities were achieved with the use of (1R,2R)‐15 a–c. This technique was used to synthesize (R)‐(−)‐baclofen
新的氯霉素基硫脲有机催化剂(1 S,2 R)-12 a - f和(1 R,2 R)15 a - c的合成及其在介孔酸酐的对映选择性醇解中的应用描述。特别是,如果使用低负荷的(1 S,2 R)-12 a – f负载,半酯具有出色的对映选择性。使用(1 R,2 R)‐ 15 a – c几乎没有达到对映选择性。该技术用于合成(R)-(-)-baclofen。
Squaramide-Linked Chloramphenicol Base Hybrid Catalysts for the Asymmetric Michael Addition of 2,3-Dihydrobenzofuran-2-carboxylates to Nitroolefins
of hybrid catalysts incorporating chloramphenicol base with another chiral scaffold using a squaramide linker have been developed and successfully applied in Michael addition of 2,3-dihydrobenzofuran-2-carboxylates to nitroolefins. The controlling experiments suggested that the hybrid catalysts were more reactive than non-hybridized bifunctional catalysts and the matching of chiralities between two
Density Functional Theory Calculations of the Optical Rotation and Electronic Circular Dichroism: The Absolute Configuration of the Highly Flexible <i>trans</i>-Isocytoxazone Revised
作者:Marcin Kwit、Maria D. Rozwadowska、Jacek Gawroński、Agnieszka Grajewska
DOI:10.1021/jo901175s
日期:2009.11.6
that the most frequently used B3LYP/6-31G(d) method is not adequate for prediction of the absoluteconfiguration of this type of highlyflexible molecules. The absoluteconfigurations of levorotatory trans-isocytoxazone 2 and analogues 1, 3, and 4 have been established as (−)-(4S,5S)-trans-1−4; i.e., it is in opposition to the previously published configuration (−)-(4R,5R)-trans-2.