Sequential Homoaldolization-Cuprate Rearrangement in a Stereoselective Synthesis of Stannyl Dienes: Application to the Synthesis of the Western C10-C15 Subunit of (+/-)-Tylosin Aglycon

Article abstract of DOI:10.1021/jo00117a007

A stereospecific synthesis of stannyl diene 5, corresponding to the C10-C15 fragment of (+/-)-tylosin aglycon 2, was reported.Silyl carbamate 16, submitted to the Hoppe homoaldolization conditions with propanal, gave the anti aldol product 17 in 89percent yield.Further treatment including oxidation of the silyl group led to lactone 21.The corresponding dihydrofuran 23 was then transformed into vinylstannane 25, via an efficient Kocienski rearrangement.An iodide exchange was performed on 25 and followed by a Stille coupling reaction with tributylstannyl acetylide.Stannyl cupration of the resulting silylated enyne 27 led in 44percent yield to a 1:1 mixture of the desired (E,E)-stannyl diene 5b and the unexpected (E,Z) isomer 29.The same reaction performed on desilylated enyne 28 delivered in 85percent yield the pure (E,E)-stannyl diene 5.