I've found the following works for pyruvoyl residues

top_heav.lib entry: RESI PVL 0.00000 ATOM O2 O -0.5500 ATOM C3 CD 0.5500 ATOM C2 CD 0.6000 ATOM O3 O -0.5500 ATOM C1 CT3 -0.1500 DELE ATOM N BOND O2 C2 C2 C1 C2 C3 C3 O3 C3 +N IMPR C1 C2 C3 +N IMPR O3 C3 C2 O2 IC O3 C3 C2 O2 1.2355 116.9032 15.0961 120.8798 1.2270 IC C1 C3 C2 O2 1.5090 128.5815 -171.5204 120.8798 1.2270 IC +N O2 C2 C3 1.3535 122.1373 175.9258 120.8798 1.4157 PATC FIRS NONE LAST NONE

restyp.lib entry: 142 | PVL | O | PVL | pyruvoyl