In the Aliens universe do the xenomorphs attack the synthetics?
At the end of Aliens (1986), we can see a xenomorph killing Bishop the synthetic. But in this case I think that the xenomorph killed him because it was close to humans (Ripley, ...) In the same movie Bishop had walked through the entire station without being spotted by xenomorphs.
Any explanation ?
He doesn't walk through the entire station any more than the rest of them do, while they're all in relative safety in, e.g., Medlab or Operations. He crawls through a pipe to get to the uplink, into which no grown alien would fit, and then gets to stand outside in the rain, where no alien wants to be; they like warm cozy places.
I may be synthetic, but I'm not stupid.
That quote tells us that he knows he's putting himself in danger, but as he's the only one qualified to remote pilot the ship, if he wants off that rock, then he's got to go do it.
Aliens will not hesitate to kill any creature that they deem an immediate threat, including humans. It's not shown onscreen, but I doubt that Burke is still a viable host after having an alien's second mouth penetrate his head or torso.
At the end of Aliens, she's only got one egg left in her (presumably, given the sound bite at the end of the credits), so she probably would have killed Ripely and Bishop (whether or not she could tell he was a synth) and have gone for the adolescent; the easy to subdue target.
Unless she was just out for blood. In either case the answer is: yes, absolutely. And as Bishop says, he's not stupid and he never puts himself in a situation like Burke does. Had he been in the wrong place at the wrong time like Burke was, I'm sure it would have been him who took a mouth to the head.
According to "Alien: Labyrinth" xenomorphs don't attack synthetics unless they feel threatened by them. But then this statements comes from a) unreliable narrator (Dr. Paul Church seems to be lying all the time... probably also about his imprisonment inside the hive) and b) it's not exactly canon.
In the "Alien vs Predator" games syntetics were invisible to the special alien's sight, which might suggest that in normal circumstances xenomorphs would ignore them like i.e. carnivore ignoring plants.
