Amino-Protecting Groups Subject to Deblocking under Conditions of Nucleophilic Addition to a Michael Acceptor. Structure−Reactivity Studies and Use of the 2-(tert-Butylsulfonyl)-2-propenyloxycarbonyl (Bspoc) Group
摘要:
A new type of amino-protecting group is described in which a Michael acceptor is incorporated into the protectant so that treatment with a nucleophile will trigger deblocking. Comparison of various Michael accepters showed that for several key electron-withdrawing groups, the order of reactivity was C6H5SO2 > Me3CSO2 > COOEt > CsH5SO > C(6)H(4)NO(2-)p. The reactivity of the nucleophile. (e.g., primary and secondary aliphatic amines) followed an order related to both intrinsic basicity and steric effects. beta-Substituents in the Michael acceptor caused significant retardation of the deblocking process. The Bspoc function was chosen for initial elaboration into a practical system for use in peptide synthesis. Bspoc amino acid chlorides were used as coupling agents and silica-tethered secondary amines as deblocking agents. With the latter, deblocking occurs cleanly and no byproducts remain in the organic solvent in which the deblocking is executed.
Amino-Protecting Groups Subject to Deblocking under Conditions of Nucleophilic Addition to a Michael Acceptor. Structure−Reactivity Studies and Use of the 2-(tert-Butylsulfonyl)-2-propenyloxycarbonyl (Bspoc) Group
摘要:
A new type of amino-protecting group is described in which a Michael acceptor is incorporated into the protectant so that treatment with a nucleophile will trigger deblocking. Comparison of various Michael accepters showed that for several key electron-withdrawing groups, the order of reactivity was C6H5SO2 > Me3CSO2 > COOEt > CsH5SO > C(6)H(4)NO(2-)p. The reactivity of the nucleophile. (e.g., primary and secondary aliphatic amines) followed an order related to both intrinsic basicity and steric effects. beta-Substituents in the Michael acceptor caused significant retardation of the deblocking process. The Bspoc function was chosen for initial elaboration into a practical system for use in peptide synthesis. Bspoc amino acid chlorides were used as coupling agents and silica-tethered secondary amines as deblocking agents. With the latter, deblocking occurs cleanly and no byproducts remain in the organic solvent in which the deblocking is executed.
Allylsilanes in organic synthesis; convenient preparation of synthetic intermediates by catalytic hydrosilation of acetylenic alcohols
作者:Patrick J. Murphy、John L. Spencer、Garry Procter
DOI:10.1016/s0040-4039(00)94428-9
日期:1990.1
Synthetically useful vinylslane-alcohols such as (1) can be easily prepared by the catalytic hydrosilation of the appropriate acetylenic alcohols in high yield, and with excellent regioand stereoselectivity, without the need to protect the hydroxyl group.