WELPSA: A natural catalyst of alkali and alkaline earth metals for the facile synthesis of tetrahydrobenzo[b]pyrans and pyrano[2,3‐d]pyrimidinones as inhibitors of SARS‐CoV‐2

Abstract

Since 2019, the infection of SARS‐CoV‐2 has been spreading worldwide and caused potentially lethal health problems. In view of this, the present study explores the most commodious and environmentally benign synthetic protocol for the synthesis of tetrahydrobenzo[ b ]pyran and pyrano[2,3‐ d ]pyrimidinones as SARS‐CoV‐2 inhibitors via three‐component cycloaddition of aromatic aldehyde, malononitrile, and dimedone/barbituric acid in water. Lemon peel from juice factory waste, namely, lemon ( Citrus limon ), sweet lemon ( C. limetta ), and Kaffir lime or Citron ( C. hystrix ), effectually utilized to obtain WELPSA, WESLPSA, and WEKLPSA, respectively, for the synthesis of title compounds. The catalyst was characterized by scanning electron microscope (SEM) and energy‐dispersive x‐ray spectroscopy (EDX). The concentration of sodium, potassium, calcium, and magnesium in the catalyst (WELPSA) was determined using atomic absorption spectrometry (AAS). The current approach manifests numerous notable advantages that include ease of preparation, handling and benignity of the catalyst, low cost, green reaction conditions, facile workup, excellent yields (93%–97%) with extreme purity, and recyclability of the catalyst. Compounds were docked on the crystal structure of SARS‐CoV‐2 (PDB: 6M3M). The consensus score obtained in the range 2.47–4.63 suggests that docking study was optimistic indicating the summary of all forces of interaction between ligands and the protein.

Recent advancements in the multicomponent synthesis of heterocycles integrated with a pyrano[2,3-d]pyrimidine core

“…Nesaragi et al 62 have developed the multicomponent synthesis of tetrahydro-2 H -pyranopyrimidines through a green protocol under catalytic conditions. Therefore, reactions of aryl aldehydes with malononitrile, and barbituric acid, applying WELPSA “obtained from lemon ( Citrus limon )” as an efficient catalyst, yielded the anticipated products 11a–j in remarkable yields ( Scheme 6 ).…”

Chitosan‐ZnO: An Efficient and Recyclable Polymer Incorporated Hybrid Nanocatalyst to Synthesize Tetrahydrobenzo[b]pyrans and Pyrano[2,3‐d]pyrimidinones under Microwave Expedition

“…[25][26][27][28] 4H-Chromene derivatives display pharmaceutical properties such as hypotensive, antimicrobial, antitumor, antileishmanial, anti-HIV and local anaesthetic agents. [29] 4H-Chromenes bearing amino and nitrile groups are more potent as anticancer agents. Additionally, a variety of functionalized 4H-chromene derivatives emerge as the key building blocks of various oxygencontaining natural products that possess miscellaneous biological and pharmacological activities such as antiallergic,…”

“…4 H ‐Chromene derivatives display pharmaceutical properties such as hypotensive, antimicrobial, antitumor, antileishmanial, anti‐HIV and local anaesthetic agents [29] . 4 H ‐Chromenes bearing amino and nitrile groups are more potent as anticancer agents.…”

Green Synthesis of Novel Triazolothiadiazine‐Coumarins Catalyzed by Agro Waste Extract: An Approach towards In‐Silico and In‐Vitro Anti‐Fungal Activity

“…The catalyst WELPSA and its significance in organic synthesis has earlier been reported from our laboratory. [2][3][4][5][6] Heterocycles comprising amino and mercapto groups collectively can be considered as constructive intermediates in organic synthesis. [7] In various pharmaceutical preparations heterocycles with nitrogen and sulfur are the structural units, encompassing antifungal drugs used for persistent infectivity.…”

“…This catalyst has a very significant role in the synthesis as it is generated from agro‐waste, it can be regenerated and also can be used to prepare many metal nanoparticles and has many biological significances. The catalyst WELPSA and its significance in organic synthesis has earlier been reported from our laboratory [2–6] …”