Addition of lithiated 1-benzyloxyallene to a d-arabinose-derived cyclic nitrone occurred with perfect diastereoselectivity furnishing a bicyclic 1,2-oxazine derivative, which is an excellent precursor for pyrrolizidine alkaloids hydroxylated at C-7 with optional configuration at this stereogenic center. Depending on the stage of the NO bond cleavage and ring re-closure, 7- hydroxypyrrolizidines with 7R or 7S configuration were obtained, as a result of completely selective addition reactions occurring complementarily at the bottom or top face of the endocyclic CC double bond in six- and fivemembered B rings, respectively. Applicability of these stereodivergent routes to obtain polyhydroxy pyrrolizidine alkaloids is demonstrated by the efficient syntheses of casuarine and australine as examples of the two classes of diversely configured 7-hydroxypyrrolizidine alkaloids. An alternative synthesis of australine and two strategies for the preparation of 7-epiaustraline are also reported, which demonstrate that the stereoselectivity of hydride reduction of an exocyclic CO double bond is independent of the ring size, occurring preferentially from the top face either in a six- or five-membered ring.

Stereocomplementary Routes to Hydroxylated Nitrogen Heterocycles: Total Syntheses of Casuarine, Australine, and 7-epi-Australine / Camilla Parmeggiani; Francesca Cardona; Leonardo Giusti; Hans-Ulrich Reissig; Andrea Goti. - In: CHEMISTRY-A EUROPEAN JOURNAL. - ISSN 0947-6539. - STAMPA. - 19:(2013), pp. 10595-10604. [10.1002/chem.201301320]

Stereocomplementary Routes to Hydroxylated Nitrogen Heterocycles: Total Syntheses of Casuarine, Australine, and 7-epi-Australine

PARMEGGIANI, CAMILLA;CARDONA, FRANCESCA;GOTI, ANDREA
2013

Abstract

Addition of lithiated 1-benzyloxyallene to a d-arabinose-derived cyclic nitrone occurred with perfect diastereoselectivity furnishing a bicyclic 1,2-oxazine derivative, which is an excellent precursor for pyrrolizidine alkaloids hydroxylated at C-7 with optional configuration at this stereogenic center. Depending on the stage of the NO bond cleavage and ring re-closure, 7- hydroxypyrrolizidines with 7R or 7S configuration were obtained, as a result of completely selective addition reactions occurring complementarily at the bottom or top face of the endocyclic CC double bond in six- and fivemembered B rings, respectively. Applicability of these stereodivergent routes to obtain polyhydroxy pyrrolizidine alkaloids is demonstrated by the efficient syntheses of casuarine and australine as examples of the two classes of diversely configured 7-hydroxypyrrolizidine alkaloids. An alternative synthesis of australine and two strategies for the preparation of 7-epiaustraline are also reported, which demonstrate that the stereoselectivity of hydride reduction of an exocyclic CO double bond is independent of the ring size, occurring preferentially from the top face either in a six- or five-membered ring.
2013
19
10595
10604
Camilla Parmeggiani; Francesca Cardona; Leonardo Giusti; Hans-Ulrich Reissig; Andrea Goti
File in questo prodotto:
File Dimensione Formato  
ChemEurJ2013,19,10595-10604.pdf

Accesso chiuso

Tipologia: Versione finale referata (Postprint, Accepted manuscript)
Licenza: Tutti i diritti riservati
Dimensione 345.58 kB
Formato Adobe PDF
345.58 kB Adobe PDF   Richiedi una copia

I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/822952
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 58
  • ???jsp.display-item.citation.isi??? 54
social impact