Synthesis of aza-derivatives of tetrahydrofuran lignan natural products

Modular Synthesis and Biological Investigation of 5-Hydroxymethyl Dibenzyl Butyrolactones and Related Lignans

“…We have previously shown that the acyl-Claisen rearrangement can be used to prepare disubstituted morpholine pentenamides 5 with high diastereoselectivity at the C-3 and C-4 positions which correspond to the benzyl groups in the lactone scaffold (Figure 2) [18,19,20,21,22]. Furthermore, in our efforts to a prepare a number of different lignan scaffolds [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36], we have used amides such as 5 to prepare compounds including tetrahydrofuran lignans (e.g., galbelgin 6 ), aryltetralins (e.g., ovafolinin 7 ) and aryl dihydronaphthalene lignans (e.g., (−)-pycananthuligene B 8 ).…”

An acyl-Claisen/Paal-Knorr approach to fully substituted pyrroles

“…[15][16][17][18][19] The reaction involves the in situ generation of a ketene from an acid chloride, and the subsequent [3,3] sigmatropic rearrangement of the ketene with an allylic amine yields syn-amides in >95% diastereomeric excess over the anti-products. [20][21][22] We therefore proposed that a synthetic route encompassing this reaction could be used to access syn-diketones and thus the pyrrole core with high efficiency.…”

Oxidative Transformations of Lignans

“…Oxidation of lignans baring benzylic or aliphatic hydroxyls to the corresponding ketones by DMP have been described for various lignans [81,82,83,84,85,86]. An example is shown in Scheme 20 for oxidation of isopicrosteganol to the atropisomers of picrosteganone [87].…”