I found any chemical drawing software under linux, like XDrawChem or bkchem, was no better than IsisDraw. The standalone edition IsisDraw2.5 is free to download and use. By using wine, you actually can use it as well in linux. Here is the trick. After installing wine, use winecfg to swith the simulated OS to win98. And you need to install this dcom98.exe. Copy mdlctl32.dll from /program files/common file/IsisDraw to the current directory. Then you can run it smoothly.
For SciFinder, you can run it under linux as well. But to fit the font, you need first run winecfg to swith the OS to winXP.
Have fun.