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Synthetic and spectroscopic studies on the structures of uniflorines A and B: structural revision to 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine alkaloids

Journal Article


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Abstract


  • The diastereoselective synthesis of the C-2 epimer and the C-1, C-2 di-epimers of the putative structure of the alkaloid uniflorine A has been achieved. The synthesis of the latter di-epimers employed a novel pyrrolo[1,2-c]oxazin-1-one precursor to allow for the reversal of π-facial diastereoselectivity in an osmium(VIII)-catalyzed syn-dihydroxylation (DH) reaction. The NMR spectral data of these epimeric compounds and that of related isomers did not match that of the natural product. From a comparison of the NMR data of uniflorines A and B with that of casuarine and the known synthetic 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine isomers we concluded unequivocally that uniflorine B is the known alkaloid casuarine. Although we cannot unequivocally prove the structure of uniflorine A, without access to the original material and data, the published data suggest that the natural product is also a 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine with the same relative C-7–C-7a–C-1–C-2–C-3 stereochemistry as casuarine. We thus suggest that uniflorine A is 6-epi-casuarine.

UOW Authors


  •   Davis, Andrew S. (external author)
  •   Ritthiwigrom, Thunwadee (external author)
  •   Pyne, Stephen

Publication Date


  • 2008

Citation


  • Davis, A. S., Ritthiwigrom, T. & Pyne, S. G. (2008). Synthetic and spectroscopic studies on the structures of uniflorines A and B: structural revision to 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine alkaloids. Tetrahedron, 64 (21), 4868-4879.

Scopus Eid


  • 2-s2.0-42249087299

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=8667&context=scipapers

Ro Metadata Url


  • http://ro.uow.edu.au/scipapers/5321/

Number Of Pages


  • 11

Start Page


  • 4868

End Page


  • 4879

Volume


  • 64

Issue


  • 21

Place Of Publication


  • http://www.elsevier.com/locate/tet

Abstract


  • The diastereoselective synthesis of the C-2 epimer and the C-1, C-2 di-epimers of the putative structure of the alkaloid uniflorine A has been achieved. The synthesis of the latter di-epimers employed a novel pyrrolo[1,2-c]oxazin-1-one precursor to allow for the reversal of π-facial diastereoselectivity in an osmium(VIII)-catalyzed syn-dihydroxylation (DH) reaction. The NMR spectral data of these epimeric compounds and that of related isomers did not match that of the natural product. From a comparison of the NMR data of uniflorines A and B with that of casuarine and the known synthetic 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine isomers we concluded unequivocally that uniflorine B is the known alkaloid casuarine. Although we cannot unequivocally prove the structure of uniflorine A, without access to the original material and data, the published data suggest that the natural product is also a 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine with the same relative C-7–C-7a–C-1–C-2–C-3 stereochemistry as casuarine. We thus suggest that uniflorine A is 6-epi-casuarine.

UOW Authors


  •   Davis, Andrew S. (external author)
  •   Ritthiwigrom, Thunwadee (external author)
  •   Pyne, Stephen

Publication Date


  • 2008

Citation


  • Davis, A. S., Ritthiwigrom, T. & Pyne, S. G. (2008). Synthetic and spectroscopic studies on the structures of uniflorines A and B: structural revision to 1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine alkaloids. Tetrahedron, 64 (21), 4868-4879.

Scopus Eid


  • 2-s2.0-42249087299

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=8667&context=scipapers

Ro Metadata Url


  • http://ro.uow.edu.au/scipapers/5321/

Number Of Pages


  • 11

Start Page


  • 4868

End Page


  • 4879

Volume


  • 64

Issue


  • 21

Place Of Publication


  • http://www.elsevier.com/locate/tet