20730-59-0Relevant academic research and scientific papers
Enantioselective Desymmetrization of 2-Aryl-1,3-propanediols by Direct O-Alkylation with a Rationally Designed Chiral Hemiboronic Acid Catalyst That Mitigates Substrate Conformational Poisoning
Estrada, Carl D.,Ang, Hwee Ting,Vetter, Kim-Marie,Ponich, Ashley A.,Hall, Dennis G.
, (2021/04/07)
Enantioselective desymmetrization by direct monofunctionalization of prochiral diols is a powerful strategy to prepare valuable synthetic intermediates in high optical purity. Boron acids can activate diols toward nucleophilic additions; however, the design of stable chiral catalysts remains a challenge and highlights the need to identify new chemotypes for this purpose. Herein, the discovery and optimization of a bench-stable chiral 9-hydroxy-9,10-boroxarophenanthrene catalyst is described and applied in the highly enantioselective desymmetrization of 2-aryl-1,3-diols using benzylic electrophiles under operationally simple, ambient conditions. Nucleophilic activation and discrimination of the enantiotopic hydroxy groups on the diol substrate occurs via a defined chairlike six-membered anionic complex with the hemiboronic heterocycle. The optimal binaphthyl-based catalyst 1g features a large aryloxytrityl group to effectively shield one of the two prochiral hydroxy groups on the diol complex, whereas a strategically placed "methyl blocker"on the boroxarophenanthrene unit mitigates the deleterious effect of a competing conformation of the complexed diol that compromised the overall efficiency of the desymmetrization process. This methodology affords monoalkylated products in enantiomeric ratios equal or over 95:5 for a wide range of 1,3-propanediols with various 2-aryl/heteroaryl groups.
Enzymatic desymmetrization of prochiral 2-substituted-1,3-diamines: Preparation of valuable nitrogenated compounds
Rios-Lombardia, Nicolas,Busto, Eduardo,Garcia-Urdiales, Eduardo,Gotor-Fernandez, Vicente,Gotor, Vicente
supporting information; experimental part, p. 2571 - 2574 (2009/07/25)
A wide range of prochiral 1, 3-diamines were first efficiently synthesized and subsequently desymmetrized by using lipase from Pseudomonas cepacia as catalyst and diallyl carbonate as alkoxycarbonylating agent. In all cases, the amino carbamates of R-configuration were recovered. Final selective cleavage of the N-allyloxycarbonyl moiety was carried out under mild reaction conditions, which demonstrates the high versatility and potential of this chemoenzymatic route as a source of intermediates in the synthesis of related optically active nitrogenated derivatives.
Diastereoselective synthesis of ω-phosphonic acid analogues of 4-arylkainoids
Yuasa, Yoko,Fujimaki, Nobuko,Yokomatsu, Tsutomu,Ando, Jun,Shibuya, Shiroshi
, p. 3577 - 3584 (2007/10/03)
Radical cyclisation by the use of α,β-unsaturated phosphonate as a radical acceptor was applied to a synthesis of 7-phosphonomethylpyrrolo[1,2-c]oxazolidinones, synthetic intermediates on the route to phosphonic acid analogues of kainoids. The relative configuration at the 6;7;7a-positions was found to be highly controlled by steric effects due to the substituent at the 6-position. Thus, diethyl [{(6S*,7R*,7aS*)-6-(2-methoxyphenyl)-3-oxoperhydropyrrolo[1,2- c]-[1,3]oxazol-7-yl}methyl]phosphonate 29a and diethyl [{(6S*,7R*,7aS*)-3-oxo-6-phenylperhydropyrrolo[1,2-c][1,3]- oxazol-7-yl}methyl]phosphonate 29b were prepared with high diastereoselectivity. When the substituent at the 6-position is a 1-naphthyl group, the diethyl [{(6S*,7R*,7aS*)-6-(1-naphthyl)pyrroloxazol-7-yl}methyl] phosphonate 29c and its (6S*,7R*,7aR*)-isomer 30c were formed in the ratio 29c:30c～2:1. The stereostructure of compound 29a was determined by X-ray crystallographic analysis. The 6-o-methoxyphenyl derivative 29a was converted into the corresponding phosphonic acid analogue 33.
