This invention is directed to a method for treating a host infected with hepatitis B comprising administering an effective amount of an anti-HBV biologically active 2-deoxy–L-erythro-pentofuranonucleoside or a pharmaceutically acceptable salt or prodrug thereof, wherein the 2-deoxy–L-erythro-pentoftiranonucleoside has the formula: . This then permits a better definition to run a high pressure reactor to reduce the likelihood of phase separation, loss of cooling and potentially decomposition of the reactor contents. The drive assembly comprises a spool valve rotatably positioned within the central bore and coupled to the shaft by a key.