“…Structures of known compounds, 1a , 1b , 1c , 1d , 1e , 1f , 1g , 1h , 1i , 1k , 1l , 2a , 2b , 2c , 2d , 2e , 2f , 2g , 2h , 2j , 2k , 2l , 2m , 3a , 3b , 3c , 3d , 3e , 3f , 3h , 3i , and 3l ,were confirmed by NMR spectral comparison with literature data.…”