Synthesis of Optically Active β,γ-Unsaturated α-Amino Acids and of α,β-Unsaturated γ-Amino Acids. SN2- vs. SN2’-Dichotomy of the Mitsunobu Amination of Allylic Alcohols
作者:Johann Mulzer、Günther Funk
DOI:10.1055/s-1995-3847
日期:1995.1
Novel and efficient syntheses (6-9 steps, overall yields 10-30%) are described for optically pure β,γ-unsaturated α-amino acids and α,β-unsaturated γ-amino acids, starting from (R)-isopropylidene glyceraldehyde and ethyl (S)-lactate, respectively. The key step is the Mitsunobu reaction of chiral secondary allylic alcohols with phthalimide as the nucleophile, where α,γ allylic transpositions are observed for the first time. The structure-α,γ-ratio-relationship is studied and also the stereochemistry of the allylic transposition. The α-substitution proceeds via clean SN2 inversion, whereas the γ-substitution corresponds to an (E)-anti attack of the nucleophilic with varying stereoselectivities.
Kinetic Resolution of 1,2-Diols via NHC-Catalyzed Site-Selective Esterification
作者:Bin Liu、Jiekuan Yan、Ruoyan Huang、Weihong Wang、Zhichao Jin、Giuseppe Zanoni、Pengcheng Zheng、Song Yang、Yonggui Robin Chi
DOI:10.1021/acs.orglett.8b01029
日期:2018.6.15
A kinetic resolution of 1,2-diols bearing both a secondary and a primary alcohol motif through an N-heterocyclic carbene-catalyzed oxidativeacylation reaction has been developed. A site- and enantioselective esterification reaction is involved for this process. Both the monoacylated diols obtained and the remaining enantioenriched 1,2-diols are versatile building blocks for the preparation of functional
aldehydes, catalyzed by chiral (salen)Cr(III) complexes, has been studied. The reaction proceeded smoothly for the reactive 2-oxoaldehydes and allyltributyltin in the presence of small amounts (1–2 mol %) of (salen)Cr(III)BF4 (1b) under mild, undemanding conditions. However, in the case of other simple aldehydes, the use of high-pressure conditions is required to obtain good yields. Classic chromium catalyst
The total synthesis of a novel antitumor cyclic depsipeptide FE399 was achieved mainly through the MNBA‐mediated macrolactamization. A combination of MNBA and a catalytic amount of DMAPO in the presence of triethylamine as coupling agents was found to be effective for the synthesis of the macrolactam core of FE399.
Efficient Enantioselective Synthesis of Optically Active Diols by Asymmetric Hydrogenation with Modular Chiral Metal Catalysts
作者:Renat Kadyrov、René M. Koenigs、Claus Brinkmann、David Voigtlaender、Magnus Rueping
DOI:10.1002/anie.200902835
日期:2009.9.28
Valuable vicinal 1,2‐diols can be prepared with high enantioselectivity by the asymmetric ruthenium‐catalyzed hydrogenation of aryl‐ and alkyl‐substituted α‐hydroxy ketones (see scheme). The ligands, which are distinguished by their modular construction, display excellent enantioface differentiation.