You can use this tool to convert Cinema 4D material to Octane material. The conversion process works better with simple C4D materials and you get almost the same result. However, converting the complex Cinema 4D material is a little bit tricky and you need to work on the material that is created after the conversion.
When you convert any Cinema 4D material, what Octane does is to adapt the Cinema 4D material channels to its own channels. This adaptation gives good results for some channels, but not for the others. Therefore, it may be necessary to set it manually. In the pictures below you will see which cinema 4d channel is converted to which octane channel. The table at the end of the page contains the conversion results of all channels.