Both Chase and Amex are 1:1 transfer partners with Marriott, which is in turn a 3:1 transfer partner with AS. So a roundabout, somewhat pricey way of converting your Chase/Amex points to AS miles is to first transfer to Marriott, and then transfer to AS. Every 60k Bonvoy points you transfer to AS, you get 5k bonus AS miles. So 60k Bonvoy points yields 25k AS miles total, which drops the transfer ratio to 2.4:1.