Vladimir Putin asked Bashar al-Assad, the Syrian dictator and the main Iranian ally in the Middle East, to step down. I guess Russia is hoping this would help the Russian-Turkish and the Russian-Arab relations, because Russia could stay in Syria as the guarantor that Iran will not export its oil and gas to the Mediterranean Sea through Syria. However by not supporting Bashar al-Assad Russia hurts the Russian-Iranian relations.
“Vladimir Putin asked Bashar al-Assad to go”, January 2016
http://www.ft.com/intl/cms/s/0/735b4746-c01f-11e5-9fdb-87b8d15baec2.html#axzz3xz5q4y00