Concise synthesis and confirmation of the absolute configurations of naturally occurring bioactive 2,7′-cyclolignans
A concise asymmetric synthesis of naturally occurring bioactive 2,7′-cyclolignans, namely 4,4′-dihydroxy-3′,5,5′-trimethoxy-2,7′-cyclolignan and 4,4′-dihydroxy-3,3′,5-trimethoxy-2,7′-cyclolignan, possessing the uncommon 8,8′-syn dimethyl stereochemistry and unsymmetrical C-6 units with 7′,8′-anti-or...
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| Main Authors: | , , , , |
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| Other Authors: | |
| Format: | Article |
| Published: |
2022
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| Subjects: | |
| Online Access: | https://repository.li.mahidol.ac.th/handle/123456789/76251 |
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| Institution: | Mahidol University |
| Summary: | A concise asymmetric synthesis of naturally occurring bioactive 2,7′-cyclolignans, namely 4,4′-dihydroxy-3′,5,5′-trimethoxy-2,7′-cyclolignan and 4,4′-dihydroxy-3,3′,5-trimethoxy-2,7′-cyclolignan, possessing the uncommon 8,8′-syn dimethyl stereochemistry and unsymmetrical C-6 units with 7′,8′-anti-orientation is described using a substrate-controlled stereoselective Friedel-Crafts cyclization as the key step. The products were obtained in good yields with high stereoselectivity. The absolute configurations of natural 4,4′-dihydroxy-3′,5,5′-trimethoxy-2,7′-cyclolignan and those of natural 4,4′-dihydroxy-3,3′,5-trimethoxy-2,7′-cyclolignan were assigned as (7′S,8S,8′S) and (7′R,8R,8′R), respectively, based on the experimental circular dichroism (CD) spectra of the corresponding synthesized compounds. |
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