Business? Economy? How long of a stay? UA likely won't offer you the SFO-IST-MLE. I see some options routing OGG-SFO-SIN-MLE with reasonable layovers in both directions, but they are pricey. Routing OGG-SEA-SIN-MLE with OGG-SEA on Alaska is substantially cheaper, but you won't be able to book this via UA and OGG-SEA won't earn anything with UA either.