NEW YORK (Reuters) - Sam Bankman-Fried is no "super-villain" and should not spend a "medieval" 40 to 50 years in prison as prosecutors propose, lawyers for the founder of bankrupt cryptocurrency exchange FTX said in advance of his sentencing next week.

In a court filing late on Tuesday, the 32-year-old former billionaire's lawyers said a sentence significantly lower than the 5-1/4 to 6-1/2 year guideline range they had previously proposed would be appropriate punishment for his November conviction on charges of stealing $8 billion from FTX customers.

"The memorandum distorts reality to support its precious 'loss' narrative and casts Sam as a depraved super-villain," defense lawyer Mark Mukasey wrote.

"It adopts a medieval view of punishment to reach what amounts to a death-in-prison sentencing recommendation."

Mukasey had previously said FTX customers were likely to be made whole as a result of the bankruptcy process, and that Bankman-Fried worked diligently after FTX's November 2022 collapse to recover funds before he was arrested the next month.

Bankman-Fried pleaded not guilty to seven counts of fraud and conspiracy and has vowed to appeal his conviction and sentence. In testifying at his month-long trial last year, Bankman-Fried acknowledged making mistakes while running FTX but said he never intended to steal funds.

Prosecutors disputed that in their sentencing memorandum last week, arguing Bankman-Fried gambled with his customers' money out of greed and has refused to admit that what he did was wrong.

In court filings this week, several FTX customers said they would be dissatisfied with being compensated based on the dollar value of their holdings at the time the exchange declared bankruptcy because their cryptocurrency assets would be worth much more today.

U.S. District Judge Lewis Kaplan is due to sentence Bankman-Fried at a March 28 hearing in Manhattan federal court.

(This story has been refiled to add dropped closing quote mark in the headline)