Substrate engineering Effects of different N-protecting groups in the CAL-B-catalysed asymmetric O-acylation of 1-hydroxymethyltetrahydro-beta-carbolines /

In the frame of substrate engineering, the steric effect of different N-protecting groups on the enantioselectivity and reaction rate of CAL-B-catalysed (S)-selective O-acylation of N-protected 1hydroxym-ethyl-tetrahydro-beta-carbolines was investigated. Excellent enantioselectivities (E > 200) w...

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Bibliographic Details
Main Authors: Megyesi Rita
Forró Enikő
Fülöp Ferenc
Format: Article
Published: 2018
Series:TETRAHEDRON 74 No. 21
doi:10.1016/j.tet.2018.04.012

mtmt:3396906
Online Access:http://publicatio.bibl.u-szeged.hu/14631
Description
Summary:In the frame of substrate engineering, the steric effect of different N-protecting groups on the enantioselectivity and reaction rate of CAL-B-catalysed (S)-selective O-acylation of N-protected 1hydroxym-ethyl-tetrahydro-beta-carbolines was investigated. Excellent enantioselectivities (E > 200) were observed when the acylation of N-Boc [(+/-)-l](,) N-Cbz [(+/-)-3), and N-Fmoc-protected [+/--4] substrates was performed with the use of CAL-B and acetic anhydride in toluene at 60 degrees C. The resolution of N-acetylprotected substrate +/--2 showed excellent E (>200) after 30 min, but as the reaction progressed, E started decreasing after 2 days, because of and N -> O and O -> N acly migrations. Preparative resolutions of +/--3 and +/- 4 resulted in unreacted amino alcohols (R)-3 and (R)-4 and esters (S)-7a and (S)-8a with good enantiomeric excesses (>= 88%) and high yields (>= 44%). (C) 2018 Elsevier Ltd. All rights reserved.
Physical Description:2634-2640
ISSN:0040-4020