Plant Troponoids: Chemistry, Biological Activity, and Biosynthesis

Abstract

Tropone or tropolone and its derivatives (here together called troponoids) belong to a family of natural products with a seven-membered aromatic ring and various side groups. They are mainly synthesized by plants and fungi, and most troponoids play roles of antibacterial defenses in these organisms. With an increasingly severe situation of antibiotic resistant bacteria, as well as a requirement for antifungal medicines, troponoids have attracted extensive studies since they have powerful antibacterial and antifungal activity, particularly against antibiotic-resistant bacteria. In addition, many other biological activities such as antiviral, antitumor, antioxidant, anti-inflammatory, insecticidal, or enzyme inhibitor activities are associated with troponoids. After extensive studies in the 1960s-70s, interests in natural troponoids dedclined. However, chemical and biomedical studies on troponoids bloom again from the 1990s. To date great progress has been made with troponoid study in terms of identification of new natural troponoids, chemical synthesis and properties, biological activity, biosynthesis and metabolism. Particularly, bioassay-guided screening strategy and structure-activity relation-directed structure modification and drug design has resulted in the synthesis and discovery of many new derivatives. Many of them have great promise to be developed into new medicines for their potent and specific activities. This review presents the recent advances in troponoid studies and highlights multiple faceted biological activities of troponoids, as well as their relationships with chemical structures. Chemistry, biosynthesis, and production via biotechnology of troponoids are also briefly reviewed. Applications of troponoids in daily life, agriculture, medicine, and industry, and the related patents have been considered to further extend our understanding of the increasing impact of troponoids on humans.

Carot-4-en-9,10-Diol, a Conidiation-Inducing Sesquiterpene Diol Produced by Trichoderma virens PS1-7 upon Exposure to Chemical Stress from Highly Active Iron Chelators

“…As a nonbenzenoid aromatic compound, purified tropolone possesses unique properties as a phenol and a highly active iron chelator (6,7). Before discovery of its association with symptoms of B. plantariicaused rice seedling blight, tropolone was defined as a potent antibiotic toward various bacteria and fungi (8,9).…”

Synthesis and Structure of 2-(4-Chloro-6,8-Dimethyl-1h-Quinolin-2-Yliden)-5-Tert-Butyl-3,3,3a-Trimethyl-3,3a-Dihydropentalen-1,6(2h,6ah)-Dione

“…Вместе с тем разнообразие фармакологических свойств определяется приро-дой и положением функциональных групп в тро-полоновом кольце [1]. Именно поэтому развитие методов функционализации семичленного цикла 2-гетарилзамещенных 1,3-трополонов является одной из приоритетных задач.…”

“…Предположительный механизм образова-ния 2-(6,8-диметил-4-хлор-1H-хинолин-2-или-ден)-5-трет-бутил-3,3,3a-триметил-3,3a-дигидро-пентален-1,6(2H,6aH)-диона 3 можно представить как каскадный процесс, включающий перегруппи-ровку Вагнера -Меервейна и [1,3] [1,3]-перегруппировки, в результате которой обра-зуется целевой продукт 3 (схема 1).…”

“…В условиях проведенной нами реакции [1,3]-пе-регруппировка протекает в кислой среде и, веро-ятно, инициируется термическими условиями. Учитывая невысокие выходы соединения 3 (10 %) и выделение исходного трополона 1 после заверше-ния эксперимента, можно предположить, что пере-группировка Вагнера -Меервейна в соединении 1 протекает медленно и является лимитирующей ста-дией каскадного процесса.…”

Novel Synthesis of Ureas: Application of t-Butylureas

“…The tropolone fragment can be used as a pharmacophore instead of benzoic acid, phenol or other heteroaromatic moieties, 23) and its derivatives, e.g., thujaplicins and colchicines, possess antibacterial, antifungal, antiviral, and antitumor properties. 24,25) Some tropolone derivatives show significant retinoid activity. 23) Therefore, we set out to synthesize various tropolonylureas from 5-aminotropolone (1).…”