Chiral polymethine dyes. Part 6. Synthesis, absolute configuration, UV/Vis spectroscopic, and chiroptical properties of Chiral Tri- and Pentamethinium Cyanine Dyes with 1,2,3,4-tetrahydro-3,6-dimethylquinolyl end groups

Starting with monochiral 1,2,3,4‐tetrahydro‐3,6‐dimethyl quinoline 14a,b, (Schemes 1 and 2), we have synthsized the new chiral, symmetrical and unsymmetrical, tri‐ and pentamethinium streptocyanine dyes 2a, (Scheme 8), 4a, (Scheme 5), and 5a,b, (Scheme 4), resp. 9a, (Scheme 6), 10a,b, (Scheme 4), and 11a, (Scheme 7) with one or two stereogenic centers in the two heterocyclic end groups. The absolute configuration of 14a,b, and thus the absolute configuration of all monochiral polymethinium dyes derived from 14a,b, has been determined by a single‐crystal X‐ray analysis of its 4‐bromobenzenesulfonyl derivative 17a, (Scheme 1 and Fig. 1). The UV/Vis spectroscopic and chiroptical properties of the new polymethinium dyes have been studied for the first time and compared with that of similar streptocyanine dyes synthesized earlier (Tables 1 and 2) in order to find possible correlations between chiroptical properties and molecular structure.