Registre de correu electrònic: One-pot synthesis of (1RS,21SR)-diethyl 2-[23-amino-22-eth­oxy­carbonyl-8,11,14-trioxa-25-aza­tetra­cyclo­[19.3.1.0(2,7).0(15,20)]penta­cosa-2,4,6,15(20),16,18,22-heptaen-25-yl]but-2-endioate