Zinc cis-7,8-dihydroxy-pyrobacteriochlorophyll-a lacking the 7,8-dihydrogen atoms and 132-methoxycarbonyl group was prepared by chemical modification of naturally occurring chlorophyll-a as a model of bacteriochlorophyll-a essential to anoxygenic photosynthetic bacteria. This semi-synthetic bacte-riochlorin model is readily available and chemically stable to give similar optical properties to those of bacteriochlorophyll-a in diethyl ether.