Hi,

There are indeed a couple software that you can use to generate a library of derivatives for your compound virtually (also technically known as compound library enumeration). Here are a list of these tools (note: the first link is the link to the software and the second link is the link to its corresponding reference article:

- GLARE

http://glare.sourceforge.net/

http://pubs.acs.org/doi/abs/10.1021/ci0504871

- SmiLib

http://gecco.org.chemie.uni-frankfurt.de/smilib/

http://onlinelibrary.wiley.com/doi/10.1002/qsar.200630101/abstract

- Library synthesizer

http://tripod.nih.gov/?p=370

- Chemical Library Enumeration

https://www.knime.org/knime-applications/chemical-library-enumeration

If you are into programming your own solution you can use OEChem Toolkit in Python:

http://www.eyesopen.com/oechem-tk

https://docs.eyesopen.com/toolkits/python/oechemtk/

This link lists a few of them

http://crdd.osdd.net/combi.php

DataWarrior from Actelion.

http://www.openmolecules.org/datawarrior/download.html

Unfortunately, the best available tool will be your med chem knowledge about compounds.  I have looked at thousand of compounds generated by the leading software in the field and nothing can beat common sense and med chem logics.

If you still want to take your chances, you can check this list: http://crdd.osdd.net/combi.php