Revisiting the absolute chirality and polymorphism of (–)‐Istanbulin A. Issue 9 (28th August 2020)

• Record Type: Journal Article
• Authors: Arancibia, Luz; Naspi, Mariana; Pucci, Graciela; Rodriguez, Maricel; Di Salvo, Florencia
• Is Part Of: Acta crystallographica. Volume 76:Issue 9(2020)
• Page Start: 914
• Page End: 920
• Publication Date: 2020-08-28
• Subjects: Istanbulin -- natural product -- Senecio filaginoides -- terpenoid -- crystal structure -- absolute configuration -- polymorphism -- antimicrobial activity; Crystallography -- Periodicals; Crystals -- Periodicals; 548.3
• DOI: 10.1107/S2053229620011493
• Languages: English
• ISSNs: 2053-2296

Abstract

Abstract : The natural product (−)‐Istanbulin A was isolated from Senecio filaginoides DC and the chirality is described as 4 S, 5 R, 8 R, 10 S based on single‐crystal X‐ray diffraction studies. (−)‐Istanbulin A corresponds to a polymorph of a previously reported form of (−)‐Istanbulin A (form I) and this is the first time that polymorphism has been reported in the Istanbulin family. Abstract : The terpenoid (−)‐Istanbulin A is a natural product isolated from Senecio filaginoides DC, one of the 270 species of Senecio (Asteraceae) which occurs in Argentina. The structure and absolute configuration of this compound [9a‐hydroxy‐3, 4a, 5‐trimethyl‐4a, 6, 7, 8a, 9, 9a‐hexahydro‐4 H, 5 H ‐naphtho[2, 3‐ b ]‐furan‐2, 8‐dione or (4 S, 5 R, 8 R, 10 S )‐1‐oxo‐8β‐hydroxy‐10β H ‐eremophil‐7(11)‐en‐12, 8β‐olide, C15 H20 O4 ] were determined by single‐crystal X‐ray diffraction studies. It proved to be a sesquiterpene lactone showing an eremophilanolide skeleton whose chirality is described as 4 S, 5 R, 8 R, 10 S . Structural results were also in agreement with the one‐ and two‐dimensional (1D and 2D) NMR and HR–ESI–MS data, and other complementary spectroscopic information. In addition, (−)‐Istanbulin A is a polymorph of the previously reported form of (−)‐Istanbulin A, form I; thus, the title compound is denoted form II or polymorph II. Structural data and a literature search allowed the chirality of Istanbulin A to be revisited. The antimicrobial and antifungal activities of (−)‐Istanbulin A, form II, were evaluated in order to establish a reference for future comparisons and applications related to specific crystal forms of Istanbulins.