The divergent asymmetric synthesis of kalafungin, 5-epi-frenolicin B and related pyranonaphthoquinone antibiotics
作者:Christopher D. Donner
DOI:10.1016/j.tet.2012.10.012
日期:2013.1
A divergent, asymmetric method for the synthesis of pyranonaphthoquinones is reported. The synthetic strategy applies a Staunton–Weinreb annulation between substituted ortho-toluates and the (R)-pyran-2-one 7 to construct the key naphthopyranone intermediates. Stereoselective introduction of either a methyl or propyl C5 alkyl substituent by use of Grignard addition/silane-mediated reduction and a sequence
Two new enantioselectivesyntheses of the naphthopyranquinone antibiotic frenolicin B (1), of its enantiomer 2, and of its diastereoisomers 3 and 4 were accomplished using two different routes from optically active β-Hydroxy esters (R)- and (S)-11 and 18. β-Hydroxy esters (R)- and (S)-11 were prepared stereoselectivelyfrom optically active sulfenylacetates (S)- and (R)-10, respectively (Scheme 2,