Synthesis of legonmycins A and B, C(7a)-hydroxylated bacterial pyrrolizidines

• Wilfred J. M. Lewis,
• David M. Shaw and
• Jeremy Robertson

Beilstein J. Org. Chem. 2021, 17, 334–342, doi:10.3762/bjoc.17.31

• pyrrolizidines; cyanoketones; legonmycin; vinylogous ureas; Introduction At least 40 members of the large class of pyrrolizidine alkaloids [1][2][3][4] have so far been characterized from bacterial cultures. Of these ‘bacterial pyrrolizidines’, those of the vinylogous urea type are particularly intriguing from

• ]. Contemporaneously, three further bohemamines were described [16]; five more plus a related 7a-hydroxylated variant [17], various dimeric bohemamines [18][19], and spithioneines A and B [20] extended the range more recently [21]. Almost 40 years after the bacterial pyrrolizidines were first recognized, two 2015

• methyl groups in the bohemamines and NP25302 [24]. Our interest in this area originated in reports of significant biological activity for those bacterial pyrrolizidines for which such effects have been assessed. The clazamycins, jenamidine A, dibohemamines D–F, and quinohemamine are all reported to be