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Polylithiated β‐Peptides: like ‐Selective C ‐Terminal Alkylation of Boc‐β‐HVal‐β‐HAla‐β‐HLeu‐OMe
Author(s) -
Hintermann Tobias,
Mathes Christian,
Seebach Dieter
Publication year - 1998
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199811)1998:11<2379::aid-ejoc2379>3.0.co;2-v
Subject(s) - chemistry , tripeptide , alkylation , moiety , epimer , stereochemistry , stereocenter , dipeptide , peptide , halide , medicinal chemistry , organic chemistry , enantioselective synthesis , catalysis , biochemistry
A series of N ‐Boc‐protected β‐tripeptide derivatives with or without N ‐methyl groups and with free or Me‐ester‐protected C terminus has been prepared ( 8 – 14 , 16 , 17 ). As with α‐peptides (→ A ), the β‐peptide derivatives can be polylithiated (→ B , C ). No epimerization of stereogenic centers and no β elimination (exception 17 → 24 ) is observed upon treatment with bases as strong as t BuLi. The C terminal ester Li‐enolate moiety of tetralithio β‐tripeptides (cf. C ) can be selectively alkylated with methyl, benzyl and allyl halides, and with tert ‐butyl bromoacetate in yields ranging from 35‐80% ( 8 → 18 , 14 → 20 – 23 ).