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Uma nova sintese dos enantiomeros (-)-(R)- e (+)-(S)-angustureina, assim como do racemato (±)-angustureina, a partir de um b-amino ester racemico controlado por resolucao cinetica enzimatica, e descrita. Esta estrategia permitiu, incorporar tanto o esqueleto basico como controlar o unico estereocentro no carbono 2 de ambos enantiomeros. A sequencia em cinco etapas a partir dos b-amino ester e o carboxilato de sodio quirais para a sintese de ambos os alcaloides foi feita com um rendimento global de 80 e 44%, respectivamente, e excelentes excessos enantiomericos (95 e 96%, respectivamente) e sem nenhuma protecao de grupos funcionais em todas as etapas. The present study describes a new synthesis of (-)-(R)- and (+)-(S)-angustureine enantiomers, as well as of racemate (±)-angustureine, from a racemic b-amino ester controlled by kinetic enzymatic resolution. This strategy allowed to incorporate the basic skeleton, as well as to control the single stereocenter at carbon 2 in both enantiomers. The sequence of five steps starting from the chiral b-amino ester and sodium carboxylate for the synthesis of both alkaloids achieved overall yields of 80 and 44%, respectively, and produced excellent enantiomeric excesses (95 and 96%, respectively) with no protection of functional groups in any of the steps.

Enantioselective Synthesis of both (—)-(R)- and (+)-(S)-Angustureine Controlled by Enzymatic Resolution