Page 1. Tetrahedron Letters,Vol.28,No.27,pp 3069-3070,1987 oo40-4039/87 $3.00 + .OO Printed in Great Britain Perqamon Journals Ltd. ... The addition of a quinone oxidant (DDQ at 25-C, 1 min, (31%); or p-chloranil at 61-C, 1 h (32%)) converted the porphyrinogen to ...