article chemical reaction drug synthesis stereochemistry unclassified drug Multicomponent reaction 4 Ugi reaction 4 neurosteroid 4 pregnane derivative 4 priority journal 4 17 carboxaldehyde 2 2,5 diketopiperazine derivative 2 2,5-Diketopiperazines 2 3alpha acetoxy 5beta h 11 pregnen 20 one 2 3alpha acetoxy n [2 (trimethylsilyl)ethanesulfonyl] 11alpha,12alpha aziridino 5beta h pregnan 20 one 2 3alpha benzyloxy 19 hydroxy 6 thia 5alpha pregnan 20 one 2 3alpha hydroxy 5alpha pregnan 20 one 2 3alpha hydroxy 6 thia 5alpha pregnan 20 one 2 3alpha hydroxy n methyl 11alpha,12alpha aziridino 5beta h pregnan 20 one 2 3beta hydroxy 19 formyloxy 6 thia 5alpha pregnan 20 one 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