33879-04-8Relevant articles and documents
Catalysis of the Hajos-Parrish-Eder-Sauer-Wiechert reaction by cis- and trans-4,5-methanoprolines: Sensitivity of proline catalysis to pyrrolidine ring conformation
Cheong, Paul Ha-Yeon,Houk,Warrier, Jayakumar S.,Hanessian, Stephen
, p. 1111 - 1115 (2004)
Methanoprolines are found to be catalysts for the Hajos-Parrish-Eder-Sauer- Wiechert reaction.[1] cis-4,5-Methanoproline exhibits catalytic ability similar to proline (86% yield, 93% ee), whereas the trans-4,5- methanoproline is less selective (67% yield, 83% ee) and shows less acceleration. The reaction was also studied with hybrid density functional theory (B3LYP). The nearly planar cis-4,5-methanoproline amine better reflects the planar iminium of the transition states than the pyramidalized trans4,5-methanoproline. This difference in conformation is responsible for the observed higher enantioselectivity and enhanced catalytic behavior of the cis-4,5-methanoproline.
Evolution of a Unified Strategy for Complex Sesterterpenoids: Progress toward Astellatol and the Total Synthesis of (-)-Nitidasin
Hog, Daniel T.,Huber, Florian M. E.,Jiménez-Osés, Gonzalo,Mayer, Peter,Houk, Kendall N.,Trauner, Dirk
, p. 13646 - 13665 (2015/09/22)
Astellatol and nitidasin belong to a subset of sesterterpenoids that share a sterically encumbered trans-hydrindane motif with an isopropyl substituent. In addition, these natural products feature intriguing polycyclic ring systems, posing significant challenges for chemical synthesis. Herein, the evolution of our stereoselective strategy for isopropyl trans-hydrindane sesterterpenoids is detailed. These endeavors included the synthesis of several building blocks, enabling studies toward all molecules of this terpenoid subclass, and of advanced intermediates of our initial route toward a biomimetic synthesis of astellatol. These findings provided the basis for a second-generation and a third-generation approach toward astellatol that eventually culminated in the enantioselective total synthesis of (-)-nitidasin. In particular, a series of substrate-controlled transformations to install the ten stereogenic centers of the target molecule was orchestrated and the carbocyclic backbone was forged in a convergent fashion. Furthermore, the progress toward the synthesis of astellatol is disclosed and insights into some observed yet unexpected diastereoselectivities by detailed quantum-mechanical calculations are provided. Two and a half molecules: Astellatol and nitidasin are polycyclic sesterterpenoids, posing considerable challenges for synthetic chemists. In this full account, the evolution of a synthetic strategy for these and structurally related natural products is given (see scheme). The presented work includes efforts toward a biomimetic synthesis of astellatol, a successful route for the first total synthesis of (-)-nitidasin, and quantum-mechanical investigations into unexpected diastereosectivities.
The A-CD analogue of 16β,17α-estriol is a potent and highly selective estrogen receptor β agonist
Sauvee, Claire,Schaefer, Anja,Sunden, Henrik,Ma, Jian-Nong,Gustavsson, Anna-Lena,Burstein, Ethan S.,Olsson, Roger
, p. 1439 - 1442 (2013/11/19)
Selective estrogen receptor β (ERβ) agonists display neuroprotective properties in animal models and hold promise in the treatment of neurodegenerative diseases. In our quest to design, synthesize and evaluate potent and safe ERβ agonists, we focused on m
