A concise sequential photochemical-metathesis approach for the synthesis of (+)-castanospermine and possible uniflorine-A stereoisomers

Zhao, Zhiming; Song, Lijuan; Mariano, Patrick S.

doi:10.1016/j.tet.2005.07.014

Cited by 73 publications

(33 citation statements)

References 13 publications

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“…This paper also reported the synthesis of 1,2,8a-tri-epi-1 and 8a-epi-1, these compounds also had NMR spectral data significantly different to that of uniflorine A. In 2005 Mariano 13 reported the synthesis of 1-epi-1, while 1,2-di-epi-1 was reported by Fleet 14 in 1996 (Figure 2), before uniflorine was even isolated, and later by Mariano in 2005. 13 These indolizidine molecules also had NMR spectral data different to that of uniflorine A.…”

Section: Introductionmentioning

confidence: 72%

“…10 The structure of our synthetic 1 was unequivocally established by a single-crystal X-ray crystallographic study of its pentaacetate derivative. 10 The 1 H and 13 C NMR data for synthetic 1, however did not match with those reported for uniflorine A; the latter showed many more downfield peaks in the 1 H NMR, perhaps consistent with the amine salt. The 1 H NMR of the hydrochloride salt of synthetic 1 however, did not match the literature spectral data either.…”

Section: Introductionmentioning

confidence: 81%

“…In 2005 Mariano 13 reported the synthesis of 1-epi-1, while 1,2-di-epi-1 was reported by Fleet 14 in 1996 (Figure 2), before uniflorine was even isolated, and later by Mariano in 2005. 13 These indolizidine molecules also had NMR spectral data different to that of uniflorine A. Thus if uniflorine A was epimeric at C-1 and / or C-2 with compound 1 then the only remaining possible structure for the natural product was 2-epi-1.…”

Section: Introductionmentioning

confidence: 94%

“…13 C before the addition of NaH (7.3 g, 78.98 mmol, 30% dispersion in mineral oil). The mixture was then warmed to rt and stirred for 1 h before the addition of MeOH (2 mL).…”

Section: (6e)-mentioning

confidence: 99%

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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

2008

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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. Abstract:The diasteresoselective 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-

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Section: Introductionmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 94%

“…13 C before the addition of NaH (7.3 g, 78.98 mmol, 30% dispersion in mineral oil). The mixture was then warmed to rt and stirred for 1 h before the addition of MeOH (2 mL).…”

Section: (6e)-mentioning

confidence: 99%

See 2 more Smart Citations

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

2008

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“…11,12 In a more recent effort we showed that irradiation of a basic aqueous solution of the cyclopenta-fused pyridinium perchlorate 7 results in regioselective and stereoselective generation of the tricyclic allylic alcohol 8 (Scheme 3). 13 Furthermore, we observed that 8 can be transformed to spirocyclic amino diol derivatives related to 9.…”

Section: Introductionmentioning

confidence: 99%

Observations Made in Exploring a Pyridinium Salt Photochemical Approach to the Synthesis of (+)-Lactacystin

2008

Bulletin of the Korean Chemical Society

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The key step in a strategy for the synthesis of (+)-lactacystin involving photocyclization reaction of a cyclopenta-fused pyridinium salt has been probed by using a model substrate. Observations made in this effort led to the discovery of a highly unusual cascade process that leads to stereoselective formation of an interesting tricyclic carbamate. The results of this study are presented and discussed in the context of a (+)-lactacystin synthetic approach.

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Photochemical Synthesis

Protti

Fagnoni

Albini

2012

Green Techniques for Organic Synthesis and Medicinal Chemistry

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A concise sequential photochemical-metathesis approach for the synthesis of (+)-castanospermine and possible uniflorine-A stereoisomers

Cited by 73 publications

References 13 publications

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

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

Observations Made in Exploring a Pyridinium Salt Photochemical Approach to the Synthesis of (+)-Lactacystin

Photochemical Synthesis

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