At face value, it's far from clear how this molecule was discovered. Nothing about the structure indicates that it would taste sweet. Wikipedia offers this acco

At face value, it's far from clear how this molecule was discovered. Nothing about the structure indicates that it would taste sweet. Wikipedia offers this account: > Aspartame was discovered in 1965 by James M. Schlatter, a chemist working for G.D. Searle & Company. Schlatter had synthesized aspartame as an intermediate step in generating a tetrapeptide of the hormone gastrin, for use in assessing an anti-ulcer drug candidate. He discovered its sweet taste when he licked his finger, which had become contaminated with aspartame, to lift up a piece of paper. https://en.wikipedia.org/wiki/Aspartame https://en.wikipedia.org/wiki/Aspartame But the Washington Post seems to disagree: > It has been 17 years since chemist James M. Schlatter, who was tinkering with an anti-ulcer drug at the time, dipped his finger into a mixture of asparatic acid and phenylalanine and, for reasons that remain unclear, brought the result into contact with his tongue. Now, after a long legal and scientific struggle, the stuff that was on Schlatter's finger that fateful day in 1965 can be on your finger too, or dissolved in your coffee, or stirred into your yogurt, or sprinkled over your cinnamon toast. https://www.washingtonpost.com/archive/lifestyle/food/1982/09/22/the-market-is-sweet-on-aspartame/104de9dd-ca6f-40ec-84a8-58166cf23585/ https://www.washingtonpost.com/archive/lifestyle/food/1982/0... There was a time when reporting the taste of a newly-synthesized organic molecule was not uncommon in the literature. It's possible that Schlatter was just doing something that was not unusual at the time. An account of the discovery, written by one of the authors of the original research paper reporting the discovery (Mazur), and reportedly based on an affidavit gives this account: > In December 1965 I was working with Dr. Mazur on the synthesis of the C-terminal tetrapeptide of gastrin. We were making intermediates and trying to purify them. In particular, on an occasion in December, 1965, I was recrystallizing aspartylphenylalanine methyl ester (aspartame) ... when the mixture bumped [spilled over while boiling] onto the outside of the flask. As a result, some of the powder got onto my fingers. At a slightly later stage, when licking my finger to pick up a piece of paper, I noticed a very strong, sweet taste. Initially, I thought that I mush have still had some sugar o. my hands from earlier in the day. However, I quickly realized this could not be so, since I had washed my hands in the meantime. I, therefore, traced the power on my hands back to the container into which I had placed the crystallized apsartyl-phenylalanine methyl ester. I felt that this ... was not likely to be toxic and I therefore tasted a little of it and found that it was the substance which I had previously tasted on my finger. - Aspartame: Physiology and Biochemistry, edited by Stegink and Filer