Semi-synthetic diversification of coronarin D, a labdane diterpene, under Ugi reaction conditions.

The prevalence of 5-hydroxydihydrofuran-2(3)-one moiety in natural products is exploited for the first time using coronarin D, a labdane diterpene, to afford Ugi reaction product and interrupted Ugi product . The potential of the Ugi reaction was further extended to l-phenylalanine, 2-aminopyridine, and d-glucosamine, which afforded Ugi reaction products , , and , respectively. Cytotoxicity studies in RAW cells reveal that compounds and were non-toxic up to 50 µM, and these compounds were able to reduce the LPS stimulated NO production in RAW cells in par with the standard anti-inflammatory drug dexamethasone.