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This report deals with azodyes naturalised through glycoconjugation with a very common saccharide -lactose- and with its galactose and glucose components. The conjugation takes place through a bifunctional linker, here a terminal dibromoalkane, so the final products are very stable diether derivatives of the starting dyes. These transformations produce nat uralised dyes -indeed, water-soluble and multipurpose- that are able to dye different materials without addition of chemical additives such as surface agents

a b s t r a c tCommercially available Disperse Orange 29 (1a) and Disperse Red 1 (2a) were elaborated to glycoconjugated species, following a new version of a previously-described 'naturalisation' procedure. Glutamic acid was chosen to achieve a double glycoconjugation, which is essential to give to the original disperse dye a water solubility suitable for reaching optimal dyeing conditions. UV-vis plot of the 'naturalised' species showed negligible differences when compared to those of the commercial dyes.Ó 2011 Elsevier Ltd. All rights reserved.The naturalisation of dyes 1 (i.e., the conjugation of dyes to saccharide species) has proven to be a valid method to prepare novel dyeing agents. The main characteristics of these dyes are not only their solubility in water, but also their ability to dye the majority of synthetic and natural (wool, cotton) textiles. 2 Moreover this property is accompanied by the environmentally sound characteristic: the overall process of dyeing does not require surfactants, mordants, dispersing agents or other additives, generally required to yield a good permeation of the dye into the fabrics. 3A limitation of the solubilising power of the saccharidic unit when conjugated with the dye, is that the molecular weight of the two portions must remain similar. 4 We have observed that large molecular sized dyes do not reach an acceptable hydrosolubility when glycoconjugated with a single lactose unit, despite the presence of a variety of linkers such as esters, ethers, amides, alkylamino derivatives and mixed ethereal-esters, or amido-esters. 4 To extend the field of application of this new type of dyeing agent, we studied a double glycoconjugation with lactose, bonded through a difunctional linker to the chromophore. This should enhance the solubilising power of the saccharide according to the molecular weight of the dye.As a first example of this approach we recently prepared malonic acid derivatives.1c,d Herein, we highlight that glutamic acid is a particularly convenient functionality to link chromophoric moieties to saccharides in the form of water soluble dyes. The procedure allows the preparation of new materials able to dye and to reduce the environmental impact of the waste produced by dyeing.

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Recently we started to develop a new class of dyes based upon the glycoconjugation of disperse dyes with mono-or disaccharides. We used the term "naturalised" to describe these dyes because we used natural lactose in the glycoconjugation process, and also because they are similar to real natural dyes, the hydrosolubility of which is based upon the saccharidic moiety attached to the chromophore, as in carminic acid or carthamin. Synthetic dyes submitted to the process of naturalisation consist of small chromophoric molecules, prevalently azoic, whereas larger dye molecules with a higher mass did not show appreciable solubility in water