Using the script below (paste it into your .vimrc), I just hit "\s" with the cursor on a SMILES string, and up pops its ASCII depiction (":q" to close). Need a bigger image? "\S" is your friend. This is my first Vim script ("and I hope it's your last" sez you) so if you have any improvements, let me know.
[Update 16/06/2014]: Script updated to handle quoted SMILES strings and those with escaped backslashes.
noremap <silent> <leader>s :call SmiToAscii(79)<CR> noremap <silent> <leader>S :call SmiToAscii(189)<CR> function! SmiToAscii(width) let smiles = expand("<cWORD>") " Strip quotation marks and commas let smiles = substitute(smiles, "[\"',]", "", "g") " Handle escaped backslashes, e.g. in C++ strings let smiles = substitute(smiles, "\\\\", "\\", "g") botright new setlocal buftype=nofile bufhidden=wipe nobuflisted noswapfile nowrap execute '$read ! obabel -:'.shellescape(smiles, 1). ' -o ascii -d -xa 2.0 -xw '. a:width setlocal nomodifiable 1 endfunction