Synthetics
3-mercapto-2-butanone is described as a food additive and does not have a clear odor profile.
Mosciano, Gerard P&F 26, No. 5, 68, (2001): Meaty, roasted beef, sulfurous, fried onion, with nuances of coffee and chocolate
Luebke, William tgsc, (2007): Sulfurous onion roasted gassy meaty
Blue Marble Biomaterials: Meaty, roasted beef, sulfurous, fried onion, w/ nuances of coffee and chocolate
Sigma-Aldrich: Chocolate; meaty; alliaceous (onion, garlic); coffee