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. 2004 Aug 17;101(33):12054-7.
doi: 10.1073/pnas.0402274101. Epub 2004 Jul 27.

Efficient construction of the securine A carbon skeleton

Peter Korakas  1 , Stuart Chaffee, J Brad Shotwell, Pamela Duque, John L Wood
Affiliations

Efficient construction of the securine A carbon skeleton

Peter Korakas et al. Proc Natl Acad Sci U S A. .

Abstract

Securamine A is a structurally intriguing alkaloid possessing a pyrroloindole core joined via a modified isoprene subunit to a functionalized imidazole ring. Recent synthetic efforts in this laboratory have resulted in the efficient construction of key lactone 36, which undergoes tandem azide reduction/ring expansion to macrolactam 37. Macrolactam 37 possesses the complete macrocyclic core of securamine A.

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Figures

Fig. 1.
Fig. 1.
Representative akaloids from C. papyracea.
Fig. 2.
Fig. 2.
Securine A retrosynthetic analysis.
Scheme 1.
Scheme 1.
Imidazole construction and model chlorine installation. DMF, N,N-dimethylformamide; LAH, lithium aluminum hydride; NBS, N-bromosuccinimide; THF, tetrahydrofuran.
Scheme 2.
Scheme 2.
Imidazole-assisted rearrangement.
Scheme 3.
Scheme 3.
C2-C3 functionalization and model enamide installation. TBSO, Me2tBuSiO-; DMF, N,N-dimethylformamide.
Scheme 4.
Scheme 4.
Tandem chloride installation/enamide formation.
Scheme 6.
Scheme 6.
Indole formation/C20 alkylation. DMF, N,N-dimethylformamide.
Scheme 5.
Scheme 5.
Tandem indole formation/C20 alkylation.
Scheme 7.
Scheme 7.
C2/C3 functionalization and macrocyclization. TBSCl, Me2tBuSiCl; TBSO, Me2tBuSiO-; DMF, N,N-dimethylformamide; THF, tetrahydrofuran; DMAP, 4-(dimethylamino)pyridine; TBAF, Bu4NF.
Scheme 8.
Scheme 8.
Tandem azide reduction/ring expansion. AIBN, 2,2′-azobisisobutyronitrile.
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References

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