Macro Cpurine[9]

The purine ring system occurs in such important compounds as adenine, guanine, caffeine, and uric acid. The arguments of the macro were selected such that these compounds can be typeset. Positions 1, 2, 3, 6, 7, 8, and 9 are indicated in the following diagram by the respective substituent formulas.

$\displaystyle \purine$$R1$$R2$$R3$Q$R6$Q$R7$$R8$$R9$

Arguments 1, 3, 6, 7, 9:
An argument of ``Q'' causes no action. All other argument values are used as the respective substituent formulas R1 … R9.
Argument 2:
An argument of ``D'' prints a second bond between positions 2 and 3. All other argument values cause an outside double bond to be printed at position 2 and the argument itself to be put at the end of the double bond as the substituent formula R2.
Argument 4:
An argument of ``D'' prints a second bond between positions 1 and 6. All other argument values cause no action.
Argument 5:
An argument of ``Q'' causes no action. All other argument values cause an outside double bond to be printed at position 6 and the argument itself to be put at the end of the double bond as the substituent formula R6.
Argument 8:
An argument of ``D'' prints a second bond between positions 7 and 8. All other argument values cause an outside double bond to be printed at position 8 and the argument itself to be put at the end of the double bond as the substituent formula R8.