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Synlett 1997; 1997(5): 577-579
DOI: 10.1055/s-1997-3222
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Cycloaddition of an Enantiopure Cyclic Nitrone to Maleate: Straightforward Synthesis of the Necine Base (-)-Hastanecine

Andrea Goti* , Valentina Fedi, Luca Nannelli, Francesco De Sarlo, Alberto Brandi
  • *Centro di studio C. N. R. sulla Chimica e la Struttura dei Composti Eterociclici e loro Applicazioni (CSCEA), Dipartimento di Chimica Organica “U. Schiff”, Università di Firenze, via G. Capponi 9, I-50121 Firenze, Italy, Fax 39 55 2476964; e-mail goti@chimorg.unifi.it
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Publication Date:
31 December 2000 (online)

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A formal synthesis of the necine base (-)-hastanecine, subunit of the pyrrolizidine alkaloids hastacine and punctanecine, is reported. The key intermediate 7 is synthesized in five steps from dimesylate 11, derived from L-malic acid, in 28.3% overall yield. The correct absolute stereochemistry at C7 in the target compound is attained by means of a Mitsunobu reaction on dimesylate 11. The desired stereochemistry at the remaining stereogenic centres (C1 and C7a) derives from a highly preferential exo-anti approach in the key cycloaddition of nitrone 9 (obtained with complete regiocontrol) to dimethyl maleate.

pyrrolizidine alkaloids - (-)-hastanecine - necine bases - Mitsunobu reaction - enantiomerically pure cyclic nitrones