Not possible. You could have the wheels rebuilt using the existing hubs and some clincher rims, but.. probably much more economical to simply buy a new or used set of clincher wheeels.
Damn, that's a shame, seems like my first mistake then?
Just picked up a Motobecane with tublars. when I pumped them up one exploded, so even if I sell her or break it up, i will need to sort the tyres. Are there any cheap but good options?