Credit Suisse First Boston said yesterday that it had dismissed three brokers in its San Francisco office who had been put on leave amid an investigation into the allocation of initial public offerings. The brokers were Michael Grunwald; John Schmidt, who was the head of private client services in San Francisco; and Scott Bushley, a junior-level employee. They were put on leave in March. ''They were in violation of the firm's policies and procedures,'' said a Credit Suisse spokeswoman, Jeanmarie McFadden. The three were the first to lose their jobs in connection with an investigation by the authorities into initial offerings managed by Credit Suisse and at least eight other investment banks. Investigators want to know whether Credit Suisse and other firms forced investors to make additional purchases after shares started trading or charged excessive commissions. Lawyers for the three brokers were not immediately available for comment.