Sure that was true at ww1, ww2 would be a different issue,if turkey is axis it will be invaded and occupied at the end.Ussr will want constantinple but its likely a compromise will be reached where greece will take it instead of the soviets. Also look at the border,it will be likely be very easy to take the city and fortify the coast...
The word you are looking for is I believe "Berlin". With joint Western/Soviet occupation post say 1944. No way the Soviets are going to accept Constantinople being annexed to the local extension of British foreign policy in the Eastern Mediterranean... and Greece will be very obviously that in Moscow's eyes in a TL that Venizelos won in Asia Minor.
Demetrios