Browsing Chemistry by Author "Borra, Suresh"
Chemoenzymatic Synthesis of the Antifungal Compound(–)-Pestynol by a Convergent, Sonogashira Construction of the Central Yne-DieneBorra, Suresh; Kumar, Manoj; McNulty, James; Baidilov, Daler; Hudlicky, Tomas (Wiley, 2018-10-19)A total synthesis of the fungal-derived natural prod-uct pestynol is reported via a convergent chemoenzymatic ap-proach from the readily available precursors geranyl bromide,ethyl acetoacetate, trimethylsilylacetylene, and bromobenzene. Synthetic (–)-pestynol proved to be identical in all respects to thenatural material, allowing confirmation of the structure includ-ing absolute stereochemistry.
Isolation, Synthesis, and Semi-synthesis of Amaryllidaceae Constituents from Narcissus and Galanthus sp.: De novo Total Synthesis of 2-epi-Narciclasine.Borra, Suresh; Lapinskaite, Ringaile; Kempthorne, Christine; Liscombe, David; McNulty, James; Hudlicky, Tomas (ACS, 2018-05-22)An efficient protocol for the isolation of narciclasine from common Amaryllidaceae bulbs, separation from haemanthamine, and the occurrence of a trace alkaloid, 2-epi-narciclasine are reported. Attempts to convert natural narciclasine to its C-2 epimer by Mitsunobu inversion or oxidation/reduction sequences were compromised by rearrangement and aromatization processes, through which a synthesis of the alkaloid narciprimine was achieved. The methylation of the 7-hydroxy group of natural narciclasine followed by protection of the 3,4-diol function and oxidation/reduction sequence provided the target C-2 epimer. A de novo chemoenzymatic synthesis of 2-¬epi-narciclasine from m-dibromobenzene is also described. Haemanthamine and narciprimine were readily detected in the crude extracts of Narcissus and Galanthus bulbs containing narciclasine and the occurrence of 2-epi-narciclasine as a trace natural product in Galanthus sp. is reported for the first time.