Lipase-Mediated Synthesis of Enantiopure N-Carbobenzoxy-3-hydroxy-1,2,3,4-tetrahydro- and N-Carbobenzoxy-3-hydroxy-1,2,3,6-tetrahydropyridines from 3-Hydroxypyridine
A New Preparation of HomochiralN-Protected 5-Hydroxy-3- piperidenes, Promising Chiral Building Blocks, by Palladium- Catalyzed Deracemization of Their Alkyl Carbonates
The palladium-catalyzed deracemization of N-protected alkylcarbonates of 5-hydroxy-3-piperidenes by use of chiral phosphine ligands is described. A Trost ligand such as (R)-BPA was found to be a suitable chiral ligand for the deracemization, providing N-protected 5-hydroxy-3-piperidenes in good yields with good to high enantioselectivities. A plausible mechanism for the reaction is proposed.
Conversion of chiral unsaturated cyanohydrins into chiral carba- and heterocycles via ring-closing metathesis
作者:Adrianus M.C.H. van den Nieuwendijk、Amar B.T. Ghisaidoobe、Herman S. Overkleeft、Johannes Brussee、Arne van der Gen
DOI:10.1016/j.tet.2004.07.103
日期:2004.11
Aliphatic unsaturated cyanohydrins 1-3 served as starting materials in the synthesis of a set of new chiral unsaturated cyclic 1,2-ethanolamines. Combining a Grignard addition-NaBH4 reduction sequence with a ring-closing metathesis afforded unsaturated cyclic 1,2-ethanolamines 7-11 and 22-25 in good yields and high ee (96-99%). The conversion of cyanohydrins 1-3 via a DIBAL reduction-transimination-NaBH4 reduction sequence, using allylamine, followed by ring-closing metathesis yielded tetrahydropyridines 28, tetrahydroazepinols 33 and tetrahydroazocinols 34 in high yields and excellent ee (97-99%). (C) 2004 Elsevier Ltd. All rights reserved.