After graduating and promptly joining Kidder, whose Wall Street roots went back to the 1820s, he was assigned to the Chicago office as a stock and bond salesman to institutions in Ohio, Michigan and Kentucky.
In 1954, he married Jean A. Ames, whom he had met on a Connecticut vacation. She died in 2020. In addition to their son Peter, he is survived by their two other sons, David and Thomas, and eight grandchildren. He lived in the Riverside section of Greenwich.
In Chicago, Mr. DeNunzio thrived in an era of high, fixed commissions, but soon tired of monthly marathon drives to New York on family matters. After four years, he returned to New York to work on Wall Street in Kidder’s syndicate department, which rounded up underwriting partners in offerings of new securities, mostly bonds.
Mentored by Albert H. Gordon, an éminence grise of the investment world who rebuilt Kidder after the 1929 Wall Street crash, Mr. DeNunzio quickly ascended the corporate ladder, becoming president in 1977 and chief executive in 1980.
By then the firm, reliant on traditional brokerage and underwriting as well as Mr. Siegel’s ill-gotten revenue, was in trouble.
“We were looking more like a middle-sized firm in a land of giants,” unable to compete in financing huge projects, Mr. DeNunzio recalled in the 2019 interview, at the Princeton Club in Manhattan. “Marty’s leaving shook us up,” he added, referring to Mr. Siegel. “We probably should have moved faster to build our capital.”
His resistance to new types of business earned Mr. DeNunzio the nickname “ostrich” among some younger staff members, Mr. Stewart wrote in “Den of Thieves.” Mr. DeNunzio, who said he had “acquiesced” to financial reality, wound up negotiating Kidder’s 1986 sale to the General Electric Company for $750 million. The following year, after leaving Kidder, he began a retirement marked by unusually long corporate directorships.