drug structure drug synthesis 6 unclassified drug 6 11alpha hydroxyprogesterone 3 19 hydroxy 2alpha,3alpha epoxypregnane 3 19 hydroxypregnenolone 3 acetate 3 2,19-Oxido-allopregnanolone 3 3alpha hydroxy 2,19 oxido 5alphah pregnan 20 one 3 3alpha hydroxy 5alpha pregnan 20 one derivative 3 3alpha hydroxy 5alphah pregnan 20 one 3 4,19-oxido-allopregnanolone 3 4beta,19 oxido 3alpha hydroxy 5alphah pregnan 20 one 3 Neurosteroid 3 Oxido-bridged steroid 3 article 3 bridged compound 3 conference paper 3 cyclization 3 cyclopropylketone derivative 3 dehydropregnenolone acetate 3 desilylation 3 ketone derivative 3 mercury derivative 3 neurosteroid 3 neurosteroid derivative 3 pregnenolone derivative 3 reaction analysis 3 silane derivative 3 steroid 3 structure activity relation 3