You cannot sync between two devices.
However what you can do is that use an external hard disk where you can keep all your images and the catalog.
Check this link form more information - Sharing Lightroom Catalog with Multiple Computers
Thank you. That link was very helpful. I also found this one posted on Julieanne Kost's blog. This is also helpful for short term storage on my laptop while on location.
Put all your images, the LR database (catalog) and all associated files on an external hard drive. You can sync that to as many other drives as you wish using a software utility (on Mac, SuperDuper, CCC, Chronosync etc). You can have one drive hooked up to the iMac, one that you take on location, one in a fire proof safe etc. If you take one of the drives on the road with the Macbook, at new images, just come back from location and clone that data using the above utilities back to the original drive. Be sure to set the LR preferences "Store presets with catalog" so they travel with the various drives and are not on the boot drive itself.