Stereoselective synthesis of polyether antibiotics, lasalocid A and isolasalocid A, via a chelation-controlled formation of tetrahydrofuran rings under thermodynamic conditions
of lasalocid A (6) and isolasalocid A (7) were stereoselectively constructed from the corresponding p-methoxyphenylallyl alcohols (13a, 13b) by treatment with ZnBr2 to give C13-C24 fragments (14a, 14b) via a new chelation-controlled cyclization under thermodynamic conditions. After their conversion into lasalocid ketone (19) and BOM-isolasalocid ketone (20), coupling with the C1-C11 aldehyde (22) completed
Total synthesis of the polyether antibiotic lysocellin. 2. Stereocontrolled synthesis of the C10-C23 fragment and its aldol condensation with the C1-C9 fragment to complete the total synthesis of lysocellin
C10-C23 ethyl ketone (4) was synthesized via coupling of the C16-C23 aldehyde (3) with the C11-C15 fragment (8), and subjected to the aldol reaction with the C1-C9 aldehyde (2) to complete the first stereoselective totalsynthesis of the polyether antibiotic lysocellin (1)
Chiral synthesis of polyketide-drived natural products. 43. Stereoselective synthesis of optically active 4-ethyl-3,5-dihydroxy-2-methylpentyl derivatives. A basic building block with three contiguous chiral centers of polyether antibiotics.
作者:Kiyoshi HORITA、Kazuhiro TANAKA、Osamu YONEMITSU
DOI:10.1248/cpb.41.2044
日期:——
Optically active 4-ethyl-3, 5-dihydroxy-2-methylpentyl derivatives, the iodide (4), phenyl sulfone (5), and phenyl sulfoxide (6), which are chiral synthons for an essential structural unit of polyether antibiotics, were stereoselectively synthesized starting from commercially available methyl (2S)-3-hydroxy-2-methylpropionate (7) in good overall yield (33% for 18 steps).