The structures of anticancer compounds iriomoteolide-1a and -1b were successfully determined and synthesized by researchers, highlighting their potential in cancer treatment.
A collaborative study by the research groups of Professor Haruhiko Fuwa from Chuo University and Professor Masashi Tsuda from Kochi University has resulted in the structure elucidation and total synthesis of anticancer marine natural products, iriomoteolide-1a and -1b.
These natural products were originally isolated from the marine dinoflagellate collected off the Iriomote Island, Okinawa, Japan.
Challenges in Structural Elucidation
Iriomoteolide-1a is an intriguing natural product that has attracted significant attention from the global chemical community due to its strong anticancer properties. However, it was quite challenging to determine its stereostructure using NMR spectroscopy, which is the gold standard method for structure determination of natural products.
Several chemical synthesis groups from the USA and China made intensive efforts to elucidate the stereostructure of this natural product without much success. Consequently, iriomoteolide-1a is known as “(one of) current challenging molecules for configurational assignment,” and its stereostructure has remained elusive for over a decade.
Advanced Techniques Unravel Molecular Mysteries
In this study, researchers devised an integrated approach based on NMR spectroscopic analysis, theoretical calculation, and total synthesis. Careful inspection of the authentic NMR data, with the aid of molecular mechanics-based conformational searches, helped narrow the number of candidate stereoisomers from 4,096 to just 4.
NMR chemical shift calculations suggested a single stereoisomer as the most likely structure, and its validation by total synthesis enabled successful elucidation of the stereostructure of iriomoteolide-1a for the first time. The stereostructure of iriomoteolide-1b was also determined in a similar manner.
Moreover, researchers confirmed the nanomolar cytotoxic activity of synthetic iriomotelide-1a in human cancer cells. This study paves the way for further investigations into the biological mode-of-action and structure-activity relationship of this intriguing natural product.
Implications for Future Research
More broadly, this study demonstrates the power of integrating NMR spectroscopic analysis, theoretical calculation, and total synthesis in the structure elucidation of complex natural products and will facilitate future natural product drug discovery and chemical biology.
This study was published in the Journal of the American Chemical Society.
Reference: “Iriomoteolide-1a and -1b: Structure Elucidation by Integrating NMR Spectroscopic Analysis, Theoretical Calculation, and Total Synthesis” by Tomohiro Obana, Miyu Nakajima, Kazuki Nakazato, Hayato Nakagawa, Keisuke Murata, Masashi Tsuda and Haruhiko Fuwa, 17 October 2024, Journal of the American Chemical Society.
DOI: 10.1021/jacs.4c11714
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