z-logo
Premium
Reaction of γ ‐Hydroxy‐ N ‐[1‐(dimethylcarbamoyl)ethyl]butanamides under the ‘Direct Amide Cyclization’ Conditions
Author(s) -
Iliev Boyan,
Linden Anthony,
Heimgartner Heinz
Publication year - 2006
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200690008
Subject(s) - chemistry , oxazolone , amide , azirine , crystal structure , ring (chemistry) , stereochemistry , lactone , amine gas treating , derivative (finance) , medicinal chemistry , organic chemistry , financial economics , economics
The preparation of the title compounds was achieved via the ‘azirine/oxazolone method’ starting from the corresponding γ ‐hydroxy acids. Upon subjecting the γ ‐hydroxy‐ N ‐[1‐(dimethylcarbamoyl)ethyl]butanamides 4 to the so‐called ‘direct amide cyclization’ (DAC) conditions, chlorinated acids 11 or imino lactones 12 were obtained as the sole products instead of the expected cyclodepsipeptides A or their cyclodimers ( Scheme 4). Variation of the substituents in 4 did not affect the outcome of the reaction and a mechanism for the formation of both products from the intermediate oxazolone 13 has been proposed. Under the acidic conditions of the DAC, the imino lactones are formed as their HCl salts 12 , which, in polar solvents or on silica gel, reacted further to give the chlorinated acids 11 . Stabilization of the imino lactones was achieved by increasing the substitution in the five‐membered ring, and their structure, in the form of the hydrochlorides, was established independently by X‐ray crystallography ( Fig. 4 ). A derivative 15 of the imino lactone 12a was prepared by the reaction with the 2 H ‐azirin‐3‐amine 10a ; its structure was also established by an X‐ray crystal‐structure determination ( Fig. 3 ). Furthermore, the structures of the ω ‐chloro acids 11a and 11b were determined by X‐ray crystallography ( Fig. 2 ).

This content is not available in your region!

Continue researching here.

Having issues? You can contact us here