The intermediate is the compound A. There are a couple of reasons for that: 1. The oxygen (on the phosphorus in the 5\'-adenilyc acid) with negative charge is more nucleophilic. Therefore, it would attack DCC to form the intermediate. 2. Configuration of the carbon atom (the one that bears OH and then gets into the cycle) does not change in the reaction (retention of the configuration). That supports the formation of the intermediate A. If the intermediate B participated in the reaction the oxygen atom in the cyclic AMP would have pointed up (inversion of the configuration). Solution The intermediate is the compound A. There are a couple of reasons for that: 1. The oxygen (on the phosphorus in the 5\'-adenilyc acid) with negative charge is more nucleophilic. Therefore, it would attack DCC to form the intermediate. 2. Configuration of the carbon atom (the one that bears OH and then gets into the cycle) does not change in the reaction (retention of the configuration). That supports the formation of the intermediate A. If the intermediate B participated in the reaction the oxygen atom in the cyclic AMP would have pointed up (inversion of the configuration)..