How do you select distinct() models based on a specific column with Laravel?

I have a database in which I store documents - some are independant from each other, but some are just a "next version" of a previous document. In that case, I store the id of the latest version in a column.

An example dataset would be like this:

id | name       | version | validated | latest_version_id
 1 | 'Doc 1'    |       1 |      true | null
 2 | 'Doc 2'    |       1 |      true | null
 3 | 'Doc 3 v1' |       1 |      true |    5
 4 | 'Doc 3 v2' |       2 |      true |    5
 5 | 'Doc 3 v3' |       3 |     false |    5

I would like to be able to select all validated documents in their latest version. Typically a request that would return lines 1, 2 and 4 in the dataset.

I was hoping to be able something like Docs::where('validated', true)->distinct('latest_version_id')->get() but it's obviously not as simple as that..

Any query guru to point me in the right direction? A solution would be to get all results and then filter out some models, but that doesn't sound very optimized.

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