In this paper we propose a new dynamic token-based distributed synchronization algorithm that utilizes a new technique called optimistic broadcasting (optcasting) to improve efficiency. Briefly, an optcast message is a reliable unicast one that can also be heard by nodes other than its designated destination. Our algorithm manages pending token requesters by a distributed queue, and optcasts a direction towards the current queue end to help new requesters finding the queue end more quickly. Simulated experimental results indicate that our optcast algorithm outperforms the already fast Chang-Singhal-Liu (CSL) algorithm by up to 36%, especially for large systems of many processor nodes and under high synchronization loads. In addition, optcasting is highly robust and resistant to message loss, retaining at least 63% coverage even when the message loss rate approaches 100%.