Multicomponent reaction 4 Ugi reaction article chemical reaction 4 drug synthesis stereochemistry unclassified drug 17 carboxaldehyde 2 2,5 diketopiperazine derivative 2 2,5-Diketopiperazines 2 4 (2' (1h benzo[b]azol 3 yl)ethyl) 5 n cyclohexylcarboxamido 4 aza 5alpha cholestan 3 one 2 4 (2' (1h benzo[b]azol 3 yl)ethyl) 5 n cyclohexylcarboxamido 4 aza 5beta cholestan 3 one 2 4 (2' phenylethyl) 5 n cyclohexylcarboxamido 4 aza 5alpha cholestan 3 one 2 4 (2' phenylethyl) 5 n cyclohexylcarboxamido 4 aza 5beta cholestan 3 one 2 4 (3' azidopropyl) 5 n (ethoxycarbonylmethylen)carboxamido 4 aza 5alpha cholestan 3 one 2 4 (3' azidopropyl) 5 n (ethoxycarbonylmethylen)carboxamido 4 aza 5beta cholestan 3 one 2 4 benzyl 5 n (diethoxyphosphorylmethylen)carboxamido 4 aza 5alpha cholestan 3 one 2 4 benzyl 5 n (diethoxyphosphorylmethylen)carboxamido 4 aza 5beta cholestan 3 one 2 4 benzyl 5 n (methoxycarbonylmethylen)carboxamido 4 aza 5alpha cholestan 3 one 2 4 benzyl 5 n (methoxycarbonylmethylen)carboxamido 4 aza 5beta cholestan 3 one 2 4 benzyl 5 n cyclohexylcarboxamido 4 aza 5alpha cholestan 3 one 2 4 benzyl 5 n cyclohexylcarboxamido 4 aza 5beta cholestan 3 one 2 4 butyl 5 n cyclohexylcarboxamido 4 aza 5alpha cholestan 3 one 2 4 butyl 5 n cyclohexylcarboxamido 4 aza 5beta cholestan 3 one 2 4 propargyl 5 n (ethoxycarbonylmethylen)carboxamido 4 aza 5alpha cholestan 3 one 2 4 propargyl 5 n (ethoxycarbonylmethylen)carboxamido 4 aza 5beta cholestan 3 one 2 4-Azacholestanes 2 Azasteroids 2 Azasterols 2 Heterocyclic steroids 2