Okay, so you're writing a book and you want to avoid using trademarked words so you alter them to avoid copyright infringement. For example, instead of writing McDonald's you might write 'MgRonald's' (Courtesy of "Devil's a Part-Timer!!") that's fine.
One thing that I would suggest is that you look up the name origins to companies because it would then help you to make a replacement name for your company/trademark. For instance, the company CAPITA is named that way as in capita per annum so it could be renamed to something like PERANNUM.
Also, if you want to make an AU where you want to include famous people (historical or otherwise) but because it's an AU you feel that you need to alter their names slightly - don't. Either leave the name the same or make someone up -> it's your world, therefore, your rules - it's up to you as the author to make the entire world's backstory as well as the characters'. One of the biggest readership killers is when an author changes a near-world famous person's name so that you know who they are on about but it still makes you cringe lots.
So, for the love of whatever you may believe in, please do not have an alternate universe where the Mona Lisa and Leonardo DaVinci have been changed to something like the Grona Piza and Peonardo DaGrinchi! If you did want to change Leonardo DaVinci's name for whatever reason, change it to a similar name that isn't some made up gobbledygook, like Leonard Davidson, for example.
Readers really do not want to be cringing or getting second-hand embarrassment because of poorly-written references to trademarked/well-known things, they want to be sinking their teeth into an excellent plot and well-planned out writing without breaking their focus over the sudden flaw in your work.
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The Do's and Don'ts of Book Writing
Документальная прозаHere is a guide on how to write a successful book.