Лако-красочные материалы — производство

The last two sections deal with two very important groups of terpenoid fragrance ingredients which arise, in nature, from degradation of larger units.

The sperm whale produces, in its intestinal tract, a triterpene called ambreine, the structure of which is shown in Scheme 4.37. It is not known exactly why the whale produces ambreine; it is possibly in response to some irritation. Lumps of ambreine, which can weigh up to 100 kg, are excreted into the sea. There, in the presence of salt water, air and sunlight, the ambreine undergoes a variety of degradation reac­tions to produce a complex mixture of breakdown products. The mixture is known as ambergris, from the French ambre gris (grey amber). This name arises because ambergris is found washed up on beaches, as is amber (ambre brun, brown amber), the fossilized resin, which ambergris resembles to some extent. Some of the more organo­leptically important degradation products are shown in Scheme 4.37. The most important of all is the perhydronaphthofuran, which pos­sesses the characteristic animalic note of ambergris.

Scheme 4.37

Ambergris has always been very expensive and the decline in the whale population has exacerbated the situation. The price and avail­ability of the natural material essentially preclude its use in fragrance and so, much work has been done on synthetic substitutes. The

naphthofuran is prepared from sclareol, a diterpene found in clary sage (Salvia sclarea). Clary sage oil is used in perfumery and sclareol is extracted from the distillation residues. Degradation of sclareol using permanganate gives the lactone sclareolide, as shown in Scheme 4.38. Reduction of the lactone with lithium aluminium hydride, borane or some similar reagent gives a diol which can be cyclized to the furan. This is known commercially under tradenames such as Amberlyn®, Ambrox® and Ambroxan®. In addition to the nature-identical mater­ials, there are, on the market, a number of synthetic ambergris substitutes such as Karanal®, which is described on pages 119 and 120.

Scheme 4.38