Synthesis of the acyltetronic acid ionophore tetronasin (ICI M139603)
作者:Steven V. Ley、Dearg S. Brown、J. Andrew Clase、Antony J. Fairbanks、Ian C. Lennon、Helen M. I. Osborn、Elaine S. E. StokeséOwen、David J. Wadsworth
DOI:10.1039/a804170i
日期:——
preparation of tetronasin 1, an acyltetronicacid ionophore demonstrating antibiotic, antiparasitic and growth promotion in ruminants is described. The key step involves a metal mediated cyclization reaction which creates two rings and four new stereocentres in a highly efficient manner. The configurations of three of these stereocentres are as required for the synthesis of tetronasin. The remaining stereocentre
Novel polyene cyclisation routes to the acyl tetronic acid ionophore tetronasin (ICI M139603)
作者:Geert-Jan Boons、Ian C. Lennon、Steven V. Ley、Elaine S.E. Owen、James Staunton、David J. Wadsworth
DOI:10.1016/s0040-4039(00)76543-9
日期:1994.1
An approach to the total synthesis of the ionophore antibiotic tetronasin (1) is reported, in which the key step is a novel base catalysed cascade cyslisation of an activated polyene (2). This establishes two rings and four stereogenic centres in one step. A related polyene (16) has been cyclised in a similar fashion, illustrating the generality of the procedure.
A New approach to 1,7-dioxaspiro[5.5]undec-4-enes via metallated allenol ethers. Synthesis of Lacrimin A
作者:Andrew Takle、Philip Kocieński
DOI:10.1016/s0040-4020(01)85578-2
日期:1990.1
Key steps in the first total synthesis of Lacrimin A (2) include (a) the use of methoxyallene as an enone-1,3-dianion equivalent; (b) the use of a new copper-catalysed migratory insertion reaction to construct a tri-substituted alkene stereoselectively; and (c) the use of a Pd(O)-catalysed coupling reaction to generate an isochromanone ring.
The macrolide (+)-carbonoiide B, the aglycon of the antibiotic carbomycin B, was synthesized via a convergent sequence. A key step of the approach is the union of aldehyde 6 with stannane 7 in the presence of MgBr2.OEt(2) as Lewis acid to afford the C-1-C-9 fragment 26. This chelation-controlled process uses resident stereochemistry at C-4 to control stereochemistry at C-5 and C-6. Elaboration of this fragment at both ends and incorporation of a C-11-C-15 fragment (hydroxy end 4) via esterification and intramolecular Emmons reaction was used to complete the synthesis.