A convenient synthesis of bridged azatricyclic anhydrides

A Novel Highly Selective Chiral Auxiliary for the Asymmetric Synthesis ofl- andd-α-Amino Acid Derivatives via a Multicomponent Ugi Reaction

“…With this aim, anhydride 3 was treated with benzyl alcohol in the presence of quinine to give the acid (+)- 4 which was transformed into the corresponding acyl azide via the chloroformate method. At this stage, protection of the double bond via bromine addition was fundamental to prevent competitive retro-Diels−Alder reaction during the Curtius rearrangement, , which was successfully performed in toluene at reflux in the presence of 4-methoxybenzyl alcohol on the diastereomeric mixture of dibromo derivatives 5 . Removal of double bond protection with Zn dust in the presence of a substoichiometric amount of TiCl 4 furnished the expected unsaturated carbamate (−)- 6 in an overall 80% yield from 3 .…”

Synthesis of Novel N-Heterocyclic Compounds Containing 1,2,3-Triazole Ring System via Domino, “Click” and RDA Reactions

“…133–134 °C, [α]D20 = +13 (c = 1, EtOH). 1 H and 13 C NMR data of the enantiomeric amino acids were identical with those of the racemic compounds [54,55,56,57,58,59].…”

Chemistry of Norbornane/ene and Heteronorbornane/ene β-Amino Acids

“…The dicarboxylic monoesters (43 and 44) prepared from bicyclic anhydrides 25 and 26 by methanolysis were activated by treatment with ethyl chloroformate and Et 3 N (Scheme 12). Following the addition of an aqueous solution of NaN 3 , the thermal rearrangement resulted in isocyanates; these reacted with tert-BuOH in the presence of p-toluenesulfonic acid (PTSA) to give protected amino esters, which were converted to -amino acids 45 and 46 in a quantitative yield by careful saponification with NaOH [45,46]. The intermediate isocyanates were also treated with PTSA-water to afford primary amines as key intermediates in the synthesis of potent norbornyl thromboxane TXA 2 receptor antagonists [47,48].…”

“…Thus, diexo-fused 1,3-oxazinediones 72 and 73 were coupled with di-tertbutoxycarbonate (Boc 2 O) in THF and Et 3 N, followed by the addition of glycine methyl ester, which afforded dipeptides 117 and 118 in good yields (Scheme 33) [46].…”

“…The product was heated at 150 ºC for 10 min, then purified on a by intramolecular cyclization and simultaneous cleavage of the protecting group. Followed pyrolysis yielded 1,3-oxazine-2,6-dione 74 by cycloreversion[46].…”