As far as I know, this is not possible since they are not transfer partners. If it's with United Airlines, you can transfer your miles over to Marriott points assuming you are a Silver Premier member with United. This is usually not worth it since airline miles are typically worth more but depending on the situation others may still decide it's worth it (air+hotel packages for example).
If you are just a bit short on Marriott points and that's the main reason for this transfer, you can look into several options:
1. Buying Marriott points at a rate of $12.50 per 1,000 points
2. Transfer from United Airlines miles at a ratio of 1:1
3. Transfer from Chase Ultimate Rewards Points at a ratio of 1:1
The last option is usually not worth it unless you're just transferring a small amount to meet a redemption at Marriott.
Our team has advised that Skyteam Airlines is not a partner with Marriott Rewards so they cannot be transferred.