Recherches sur la formation et la transformation des esters LXXIX [1]. Sur la réaction de l′isothiocyanate d′o‐méthoxycarbonyl‐phényle avec divers acides et l′acide sérinephosphorique

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Abstract
Amino acids devoid of «leaving groups» on their β carbon atom (neither OH: serine, nor SH: cysteine) react with o‐methoxycarbonyl‐phenyl isothiocyanate (I) in the presence of one equivalent of NaOH, in water‐dioxane or in ethanol, to yield the corresponding hydroquinazolinone derivatives II which were isolated as free acids.When treated with CH3COOH + conc. HCl the hydroquinazolinone resulting from the reaction of L‐serine with I undergoes a nucleophilic attack of the carbon bearing the leaving group OH by a lone pair of electrons of S; this attack produces the formation of an additional thiazolidine ring, yielding the thiazoloquinazolinone derivative (−)‐III. In an analogous reaction DL‐serine phosphoric acid treated with I at pH 8–9 yields the corresponding substituted hydroquinazolinone which, boiled in 1N hydrochloric acid, undergoes ring closure to (±)‐III by the same mechanism as the serine derivative (leaving group: OPO3H2).L‐Cysteine reacted with 2 equiv. of I and then treated with CH3COOH + conc. HCl gives two products: (−)‐III produced by the same mechanism as for serine (leaving group: SH), and the quinazolinone derivative IV where the SH group is also thiocarbamoylated.