Abstract: A compound of the formula ##STR1## wherein A is adenine-9-yl and X is halogen, Preferably iodine, or a pharmaceutically acceptable salt thereof. It is a novel derivative of neplanocin A and has almost the same level of cytotoxic activity. However, it is not inactivated by the action of adenosine deaminase. It is produced by replacing a hydroxyl at position-6' in neplanocin A or 2', 3'-O-protected neplanocin A with halogen by use of a halogenating agent, and when hydroxyl at position-2' or -3' is protected, removing the protective group thereof.

Abstract: Novel heterocyclic alkaloids were isolated from a marine sponge. These compounds, and derivatives thereof, are useful antifungal and antitumor compounds. The novel compounds have the following structures: ##STR1## wherein R.sub.1 =H, alkyl, alkenyl, aryl, benzyl, acyl, benzoyl, or alkali metal;R.sub.2 and R'.sub.2 =O, S, NOX, or NNHX, wherein X is alkyl or aryl.