The synthesis of (+)-nemorensic acid

Abstract

The synthesis of (+)-nemorensic acid in nine steps is described; key steps in the route were the stereoselective Birch reduction of a substituted furan, and addition of allyltrimethylsilane to an oxonium ion at C-5; an X-ray crystal structure of (2)-nemorensic acid provided proof of the relative stereochemistry of the target.

Formation of N-Boc pyrrole 2,5-methyl diester, a key intermediate in the Donohoe synthesis of 1-epiaustraline and hyacinthacine A1.

“…The Birch (Li/NH 3 ) and ammonia-free (Li/di-tert-butyl biphenyl [DBB]) 1 partial reductions, using the conditions developed by Donohoe, are applicable to a wide range of heteroaromatic compounds with a variety of substitution patterns, resulting in formation of the respective dihydro compounds in typically good to excellent yields. [2][3][4][5][6][7][8] The reduction of the N-Boc pyrrole whose formation is described herein, 9 (Figure 1) has recently been published by Donohoe et al as a key step in the routes to the biologically active natural products 1epiaustraline and hyacinthacine A 1 . 10,11 CRITICAL The methyl chloroformate should be passed through a short plug of magnesium sulfate and potassium carbonate prior to use in order to remove any residual water or acid present.…”

Formation of N-Boc pyrrole 2-ethyl ester, a key intermediate in the Donohoe synthesis of omuralide.

“…The Birch (Li/NH 3 ) and ammonia-free (Li/di-tert-butyl biphenyl [DBB]) 1 partial reductions, using the conditions developed by Donohoe, are applicable to a wide range of heteroaromatic compounds with a variety of substitution patterns, resulting in formation of the respective dihydro compounds in typically good to excellent yields. [2][3][4][5][6][7][8] The reduction of the N-Boc pyrrole whose formation is described herein, 9 (Figure 1) has recently been published by Donohoe et al as a key step in the route to the biologically active natural product omuralide. 9,10…”

Five‐Membered Heterocycles: Furan

“…Reductive methylation of furan 33 with sodium in liquid ammonia and subsequent addition of methyl iodide, on the other hand, afforded 2,5-dihydrofuran 34 (Scheme 6.16) [21].…”