نتایج جستجو برای: diastereoselectivity
تعداد نتایج: 565 فیلتر نتایج به سال:
Herein, we describe the first total synthesis of trienylfuranol A, a fungal triene-substituted tetrahydrofuran metabolite. The stereoselectivity chiral center bearing trienyl side chain was diastereodivergently controlled by addition nucleophilic species on substituted ?-butyrolactone. Remarkably, C-nucleophilic or hydride onto oxocarbenium intermediate leads to opposite diastereoselectivity re...
Abstract A strategy to control the diastereoselectivity of bond formation at a prochiral attached‐ring bridgehead is reported. An unusual stereodivergent Michael reaction relies on basic vs. Lewis acidic conditions and non‐covalent interactions re ‐ si facial selectivity en route fully substituted attached‐rings. This divergency reflects differential engagement one rotational isomer system. The...
The Ugi reaction of 2-substituted dihydrobenzoxazepines was found to proceed with unexpectedly good diastereoselectivitiy (diastereoisomeric ratios up to 9:1), despite the large distance between the pre-existing stereogenic centre and the newly generated one. This result represents the first good 1,4 asymmetric induction in an Ugi reaction as well as the first example of diastereoselective Ugi ...
β-Lactams were diastereoselectively formed by the reaction of SF5-containing aldimines, or an SF5-containing ketimine, with benzyloxyketene in a conrotatory ring closure process. Imine formation and cyclization were possible in spite of the acidification of protons on the carbon bound to SF5. The reactions of the aldimines demonstrated very good 1,2-lk diastereoselectivity, however lack of ster...
Reaction of a complex Pt organometallic species with electrophilic halogen sources in the presence of X- ligands changes the mechanism of reductive elimination from a concerted reductive coupling type to an SN2 type reductive elimination. In the absence of the added X- ligand the reductive elimination is stereoretentive; in its presence, the process is stereoinvertive. This selectivity hinges o...
Herein, we describe the concise synthesis of 2,6-cis-substituted tetrahydropyran derivatives based on a domino olefin cross-metathesis/intramolecular oxa-conjugate cyclization (CM/IOCC) reaction. We have found that the domino CM/IOCC of δ-hydroxy olefins with α,β-unsaturated carbonyl compounds (e.g., trans-crotonaldehyde or N-acryloyl-2,5-dimethylpyrrole) could be efficiently achieved in the pr...
A stereochemical study of a potentially prebiotic peptide-forming reaction was carried out as the first part of a systems chemistry investigation of potential paths for symmetry breaking. Substantial diastereomeric excesses result from a fast epimerization of the 5(4H)-oxazolone intermediate in aqueous solution.
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