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Free keywords:
alkyne metathesis;cross-coupling;hydrostannation;natural products;ruthenium
Abstract:
Countless natural products of polyketide origin have an E-configured 2-methyl-but-2-en-1-ol substructure. An unconventional entry into this important motif was developed as part of a concise total synthesis of 5,6-dihydrocineromycin B. The choice of this particular target was inspired by a recent study, which suggested that the cineromycin family of antibiotics might have overlooked lead qualities, although our biodata do not necessarily support this view. The new approach consists of a sequence of alkyne metathesis followed by a hydroxy-directed trans-hydrostannation and a largely unprecedented methyl-Stille coupling. The excellent yield and remarkable selectivity with which the signature trisubstituted alkene site of the target was procured is noteworthy considering the rather poor outcome of a classical ring-closing metathesis reaction. Moreover, the unorthodox ruthenium-catalyzed trans-hydrostannation is shown to be a versatile handle for diversity-oriented synthesis.
