I am getting following error in MacOS catelina

config.status: creating src/Makevars
** libs
/usr/local/opt/gcc/bin/g++-10 -I"/usr/local/Cellar/r/4.0.2_1/lib/R/include" -DNDEBUG  -I'/usr/local/lib/R/4.0/site-library/BH/include' -I'/usr/local/lib/R/4.0/site-library/Rcpp/include' -I/usr/local/opt/gettext/include -I/usr/local/opt/gcc/include  -I/usr/local/include/openbabel-2.0  -I/usr/include/eigen3  -DUSE_BOOST -fPIC  -g -O3 -Wall -pedantic -std=c++11 -mtune=native -pipe -c ChemmineOB.cpp -o ChemmineOB.o
ChemmineOB.cpp:1470:10: fatal error: openbabel/rand.h: No such file or directory
 1470 | #include <openbabel/rand.h>
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.
make: *** [ChemmineOB.o] Error 1
ERROR: compilation failed for package ‘ChemmineOB’
* removing ‘/usr/local/lib/R/4.0/site-library/ChemmineOB’

The downloaded source packages are in
    ‘/private/var/folders/zl/qt5w30kn7kg1h7xqj0zs166c0000gn/T/Rtmp6tufC1/downloaded_packages’
Warning message:
In install.packages(...) :
  installation of package ‘ChemmineOB’ had non-zero exit status

So you got an error saying

fatal error: openbabel/rand.h: No such file or directory

And if I google openbabel/rand.h, I get hits that indicate, unsurprisingly, that it's part of 'OpenBabel'. And if I then do another google search of 'install openbabel macos', as the first hit I get this.

This is a 'skill set' that you need to have if you are planning to do much of anything on a computer, and is something you should try to cultivate.

Can you tell me what version of ChemmineOB your trying to install? Also, can you confirm whether or not /usr/local/include/openbabel-2.0 exists on your system?