Adult African dwarf crocodiles produce an aromatic ketone called dianeackerone, named in honor of Diane Ackerman, poet champion of endangered species and biodiversity. Dianeackerone was isolated, characterized, and synthesized by J. Meinwald and co-workers at Cornell University, who found that dianeackerone occurs naturally in two stereoisomeric forms, (3S,7S ) and (3S,7R ). An outline of the synthesis of one stereoisomer of dianeackerone is shown here. 

(a) Write structures for the intermediate compounds and necessary reagents indicated by A–M below. 

(b) There is an intermediate formed on treatment of D with NBS and P(C₆H₅)₃ and before the second treatment with P(C₆H₅)₃. What is the structure of this intermediate? 

(c) Which stereoisomer of dianeackerone is formed by this synthesis? (In other words, determine the configuration of the chirality centers in the formula for dianeackerone shown below.)