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The 1α-hydroxy-A-rings of norditerpenoid alkaloids are twisted-boat conformers.

ABSTRACT: The skeletal conformations of naturally occurring norditerpenoid alkaloids fix their substituent functional groups in space, thereby directing their bioactivities. Solution conformations of the A-rings of 4 selected norditerpenoid alkaloid free bases: mesaconitine, karacoline (karakoline), condelphine, and neoline (bullatine B), were analysed by NMR spectroscopy and single-crystal X-ray crystallography. They adopt twisted-chair, twisted-boat, twisted-boat, twisted-boat conformations, respectively. That the A-ring is stabilised in a boat conformer by an intramolecular H-bond from 1α-OH to the N-ethyl tertiary amine is also confirmed in the condelphine single crystal data. The conformations are a result of through-space repulsion between 12-H_e' and atoms attached to C1 (in the equatorial positions). This causes the A-rings with 1α-OR always to be twisted whether in a chair or a boat conformation. The impact of these studies is in providing a detailed understanding of the shape of the A-ring of these important biologically active natural product alkaloids.

SUBMITTER: Zeng Z

PROVIDER: S-EPMC9053968 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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The 1α-hydroxy-A-rings of norditerpenoid alkaloids are twisted-boat conformers.

Zeng Ziyu Z Qasem Ashraf M A AMA Kociok-Köhn Gabriele G Rowan Michael G MG Blagbrough Ian S IS

RSC advances 20200518 32

The skeletal conformations of naturally occurring norditerpenoid alkaloids fix their substituent functional groups in space, thereby directing their bioactivities. Solution conformations of the A-rings of 4 selected norditerpenoid alkaloid free bases: mesaconitine, karacoline (karakoline), condelphine, and neoline (bullatine B), were analysed by NMR spectroscopy and single-crystal X-ray crystallography. They adopt twisted-chair, twisted-boat, twisted-boat, twisted-boat conformations, respectivel ...[more]

PMID: 35518334

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Dataset Information

The 1α-hydroxy-A-rings of norditerpenoid alkaloids are twisted-boat conformers.

Publications

The 1α-hydroxy-A-rings of norditerpenoid alkaloids are twisted-boat conformers.

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