excellent selectivities. This strategy also enabled access to chiral spirocyclohexene‐cyclobutanes and ‐azetidines. Additionally, the obtained scaffolds can undergo diverse transformations leading to complex structures with up to four stereocenters, and we demonstrate that the nitro group, under nucleophilic conditions, can be applied for ring‐opening of the oxetane.
Directing the Activation of Donor-Acceptor Cyclopropanes Towards Stereoselective 1,3-Dipolar Cycloaddition Reactions by Brønsted Base Catalysis
作者:Jakob Blom、Andreu Vidal-Albalat、Julie Jørgensen、Casper L. Barløse、Kamilla S. Jessen、Marc V. Iversen、Karl Anker Jørgensen
DOI:10.1002/anie.201706150
日期:2017.9.18
first stereoselective organocatalyzed [3+2] cycloaddition reaction of donor-acceptor cyclopropanes is presented. By using an optically active bifunctional Brønsted base catalyst, racemic di-cyano cyclopropylketones can be activated to undergo a stereoselective 1,3-dipolar reaction with mono- and polysubstituted nitroolefins. The reaction affords functionalized cyclopentanes with threecontiguous stereocenters
Catalytic Enantioselective Addition of Pyrazol-5-ones to Trisubstituted Nitroalkenes with an <i>N</i>
-Sulfinylurea Organocatalyst
作者:James P. Phelan、Jonathan A. Ellman
DOI:10.1002/adsc.201600110
日期:2016.6.2
The first example of enantioselective nitronate protonation following Michaeladdition of a carbon nucleophile to an α,β,β‐trisubstituted nitroalkene is reported. An N‐sulfinylurea catalyst was employed to catalyze the addition of a variety of 3‐substituted pyrazol‐5‐one nucleophiles to trisubstituted nitroalkenes incorporating an oxetane or azetidine ring at the β‐position. The nitroalkane‐pyrazolone
A simple two-step sequence is used to efficiently make novel spirocyclic analogues of the diketopiperazine nucleus. Conjugate addition of chiral -amino esters to nitroalkenes, generated from oxetan-3-one or N-Boc-azetidin-3-one, followed by nitro group reduction provides, after spontaneous cyclization, the spirocycles in good overall yields. These rigid scaffolds can be functionalized by selective N-alkylations as well as by carbonyl reduction to the corresponding piperazines.
Development of oxetane modified building blocks for peptide synthesis
作者:Stefan Roesner、Jonathan D. Beadle、Leo K. B. Tam、Ina Wilkening、Guy J. Clarkson、Piotr Raubo、Michael Shipman
DOI:10.1039/d0ob01208d
日期:——
The synthesis and use of oxetane modified dipeptide buildingblocks in solution and solid-phasepeptidesynthesis (SPPS) is reported. The preparation of buildingblocks containing non-glycine residues at the N-terminus in a stereochemically controlled manner is challenging. Here, a practical 4-step route to such buildingblocks is demonstrated, through the synthesis of dipeptides containing contiguous