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Carboxymethyl Cellulose as a Recyclable and Biodegradable Heterogeneous Catalyst for Convenient Synthesis of 2-Amino-4 <i>H</i> -chromenes
Journal
Organic Preparations and Procedures International
ISSN
1945-5453
Date Issued
2024-08-02
Author(s)
Farzaneh Mohamadpour
Hesam Kamyab
Shreeshivadasan Chelliapan
Ali Mohammad Amani
Abstract
The anti-HIV agent (±)-calanolide A (1) has been synthesized in a five-step approach starting with phloroglucinol [→ 5 → 6 → 11 → 18 → (±)-1], which includes Pechmann reaction, Friedel−Crafts acylation, chromenylation with 4,4-dimethoxy-2-methylbutan-2-ol, cyclization, and Luche reduction. Cyclization of chromene 11 to chromanone 18 was achieved by employing either acetaldehyde diethyl acetal or paraldehyde in the presence of trifluoroacetic acid and pyridine or PPTS.
Luche reduction of chromanone 18 at lower temperature preferably yielded (±)-1. Reduction of chromone 12, synthesized by Kostanecki−Robinson reaction from chromene 11, failed to afford (±)-1. The synthetic (±)-1 has been chromatographically resolved into its optically active forms, (+)- and (−)-1. The anti-HIV activities for synthetic (±)-1, as well as resultant (+)- and (−)-1, have been determined. Only (+)-1 accounted for anti-HIV activity, which was similar to the data reported for the natural product, and (−)-1 was inactive.
Luche reduction of chromanone 18 at lower temperature preferably yielded (±)-1. Reduction of chromone 12, synthesized by Kostanecki−Robinson reaction from chromene 11, failed to afford (±)-1. The synthetic (±)-1 has been chromatographically resolved into its optically active forms, (+)- and (−)-1. The anti-HIV activities for synthetic (±)-1, as well as resultant (+)- and (−)-1, have been determined. Only (+)-1 accounted for anti-HIV activity, which was similar to the data reported for the natural product, and (−)-1 was inactive.