Vinylogous Mannich reactions. Stereoselective formal synthesis of pumiliotoxin 251D
A concise synthesis of (-)-3, a known precursor of pumiliotoxin 251D, has been completed using a vinylogous Mannich reaction as a key construction. Silyloxyfuran 10 added to methoxypyrrolidine 20 in the presence of TMS-OTf to give a mixture (4.8:1) of 21 and 22 in 57% yield. Reduction and global deprotection of 21 afforded the bicyclic lactam 23. Raney Nickel mediated extrusion of the hydroxymethyl group from 23 gave (-)-3.
Synthesis of highly functionalized 2,5-disubstituted pyrrolidines via an aza-Morita-Baylis-Hillman-type reaction
An aza-Morita-Baylis-Hillman-type reaction of Michael acceptors with 5-substituted cyclic N,O-acetals derived from pyrrolidines has been investigated. It has been found that the combination of Me2S and TMSOTf work well with unhindered and reactive enals and enones whilst the use of quinuclidine and TMSOTf is superior for more hindered Michael acceptors. The reactions lead to 2,5-trans-disubstituted pyrrolidines with good to excellent diastereoselectivity. The origin of the selectivity is discussed.
Kitulagoda, James E.,Palmelund, Anders,Aggarwal, Varinder K.
supporting information; experimental part
p. 6293 - 6299
(2010/10/19)
More Articles about upstream products of 245648-23-1