text: 1. Field of the Invention
  The present invention relates to novel compounds derived from aspartame which are useful as sweetening agents and to their method of preparation.
  These novel compounds are particularly useful for sweetening a variety of products, especially drinks, foods, confectionery, pastries, chewing gums, hygiene products and toiletries, as well as cosmetic, pharmaceutical and veterinary products.
  It is known that, to be usable on the industrial scale, a sweetening agent must possess firstly an intense sweetening potency, making it possible to limit the cost of use, and secondly a satisfactory stability, i.e. a stability compatible with the conditions of use.
  2. Discussion of the Prior Art
  The dipeptide derivative N-L-.alpha.-aspartyl-phenylalanine 1-methyl ester, known by the name aspartame and having the following formula: ##STR2## is the most widely used at the present time among the sweetening agents currently on the market (U.S. Pat. No. 3,492,131). One of the great assets of this compound is its chemical constitution based on two natural amino acids, namely L-aspartic acid and L-phenylalanine. The relatively weak sweetening potency of this compound is about 120 to 180 times that of sucrose on a weight basis. Despite excellent organoleptic properties, the main disadvantages of this compound are that it is an expensive product on account of its relatively low sweetening intensity, and that it has a rather low stability under certain conditions of use of sweetening agents, especially in neutral media, limiting its areas of industrial application.
  Consequently the food industry has an apparent need for a new sweetening agent which has a high sweetening activity, so as to reduce its cost price, and which is at least as stable as aspartame, if not more stable, especially in neutral media. Thus numerous sweet dipeptides or dipeptide analogs have since been synthesized (see, for example, J. M. Janusz in Progress in Sweeteners, Ed. T. H. Grenby, Elsevier, London, 1989, pp. 1-46), but hitherto, with the exception of aspartame, none of them has seemed to satisfy the main requirements of a sweetening agent, namely excellent organoleptic properties, a sufficiently high sweetening intensity to reduce the cost of use, and a sufficient stability.