Thirty one new sodium heterosulfamates, RNHSO 3 Na, where the R portion contains mainly thiazole, benzothiazole, thiadiazole and pyridine ring structures, have been synthesized and their taste portfolios have been assessed. A database of 132 heterosulfamates (both open-chain and cyclic) has been formed by combining these new compounds with an existing set of 101 heterosulfamates which were previously synthesized and for which taste data are available.Simple descriptors have been obtained using (i) measurements with Corey-Pauling-Koltun (CPK) space-filling models giving x, y and z dimensions and a volume V CPK , (ii) calculated first order molecular connectivities ( 1 χ v ) and (iii) the calculated Spartan program parameters to obtain HOMO, LUMO energies, the solvation energy E solv and V SPARTAN . The techniques of linear (LDA) and quadratic (QDA) discriminant analysis and Tree analysis have then been employed to develop structure-taste relationships (SARs) that classify the sweet (S) and non-sweet (N) compounds into separate categories. In the LDA analysis 70 % of the compounds were correctly classified (this compares with 65 % when the smaller data set of 101 compounds was used) and in the QDA analysis 68 % were correctly classified (compared to 80 % previously). TheTree analysis correctly classified 81 % (compared to 86 % previously). An alternative Tree analysis derived using the Cerius2 program and a set of physicochemical descriptors correctly classified only 54 % of the compounds.
A data set of 101 hetero-(both cyclic and open chain) sulfamate sodium salts, whose taste data are known, have been assembled and divided into sweet (S) (20 compounds) and non-sweet (N) (81 compounds) categories. The data set is made up of 56 compounds reported earlier, 32 synthesised in this work and another 13 reported since the earlier publications. Using the parameters x, y and z (measured for the RNH portion of RNHSO 3 Na using CPK models) and first order molecular connectivity, 1 χ ν it has been possible to achieve a correct classification rate of approximately 65% using linear discriminant analysis (LDA): a compound is N if Ϫ3.285 ϩ 0.439x ϩ 0.662y ϩ 0.236z Ϫ 1.27 1 χ ν > 0 otherwise it would be S. Using quadratic discriminant analysis (QDA) the classification rate increased to approximately 80%. Finally a Tree-based analysis gave an 86% classification rate but performed poorly in classifying correctly the S group of compounds.
The effect of sulfamation on known tastants has been investigated using several series of compounds containing a primary amine function namely, nitroanilines, phenylureas and -thioureas and amino acids and peptides. Profund changes in taste took place on sulfamation. The effect of chirality on the taste portfolios of various sulfamates has also been examined by preparing sets of enantiomeric pairs from aliphatic, aliphatic/aromatic and alicyclic/aromatic precursor amines and aminoalcohols. Some interesting taste differences have emerged, though these are not as great as observed in the first study.530
Twenty four disulfamates, one trisulfamate, two tetrasulfamates and two monosulfamates have been made. The disulfamates are of two types: RN(SO 3 Na) 2 (Type A, compounds 1-20) and NaO 3 S(H)NRЈN(H)SO 3 Na (Type B, compounds 21-24) and all except three (which had not been tasted) are new materials. The positions of the -SO 3 Na groups in compounds 21-23 have been established by the use of model compounds (e.g. parent amines, appropriate monosulfamates) and 13 C-NMR. Some multisulfamation synthesis leading to compounds 25-27 has been carried out. Taste data have been obtained for almost all the sulfamates made and the significance of these in relation to structure-taste studies for sulfamate sweeteners is discussed. In particular, the possibility that the entity CHN(R)SO 3 Ϫ might function as a hydrogen source in the Shallenberger-Acree, multicomponent attachment and α-helical protein receptor mechanisms has been examined.
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