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Lateral cis-1,3,5,7-Tetraazadecalin Podands and their Complexes: Synthesis, Structure, and Strong Binding with Pb(II) and Other Heavy Metal Ions

“…Thus, benzaldehydes with electron releasing substituents (−NH 2 , −OH(R)) reacted slowly, with dehydration of the aminocarbinol intermediate, to give tetrakis-imine Schiff-bases (Scheme , part I - i: 5a , b ). These results are in agreement with earlier conclusions − in related tautomeric systems; namely, such electron donating substituents accelerate the dehydration step and stabilize the CN bond and are expected, therefore, to hinder the ring-closing step and to form stable conjugated Schiff-bases. In addition, intramolecular hydrogen bonding had been found to stabilize the open-chain Schiff-base structure …”

“…Ring–chain tautomeric equilibrium products, viz . Schiff-bases (as observed in related systems) , were also absent.…”

Two New Phenolic Amides from the Seeds of Pharbitis nil

“…It has been observed that 3 J H-4ax,H-10 is small (2.4 Hz) in cis-type of the above system while 3 J H-4ax,H-10 is large (10.3 Hz) in trans-type of the above system. 14) These data indicated that the side chain of 1 is threo-2,3-dihydroxyputrescine (threo-1,4-diamino-2,3-butanediol), NMR data of which were in agreement with those of related synthetic compounds. 14) The absolute configuration of the side chain of 1 was confirmed by acidic hydrolysis 16) that afforded threo-1,4-diamino-2,3butanediol (1b).…”

“…14) These data indicated that the side chain of 1 is threo-2,3-dihydroxyputrescine (threo-1,4-diamino-2,3-butanediol), NMR data of which were in agreement with those of related synthetic compounds. 14) The absolute configuration of the side chain of 1 was confirmed by acidic hydrolysis 16) that afforded threo-1,4-diamino-2,3butanediol (1b). 14) In order to identify its absolute configuration, 1b was converted to 2,2-dimethyl-4,5-bis(aminomethyl)-1,3-dioxolane (1c) by treatment with 2,2-dimethoxypropane and p-toluenesulfonic acid (PTSA) in MeOH (see Chart 2), 14,17) which was identical to (4S,5S)-2,2-dimethyl-4,5bis(aminomethyl)-1,3-dioxolane.…”

“…14) The absolute configuration of the side chain of 1 was confirmed by acidic hydrolysis 16) that afforded threo-1,4-diamino-2,3butanediol (1b). 14) In order to identify its absolute configuration, 1b was converted to 2,2-dimethyl-4,5-bis(aminomethyl)-1,3-dioxolane (1c) by treatment with 2,2-dimethoxypropane and p-toluenesulfonic acid (PTSA) in MeOH (see Chart 2), 14,17) which was identical to (4S,5S)-2,2-dimethyl-4,5bis(aminomethyl)-1,3-dioxolane. 18) The negative optical rotation value ([a] D 25 Ϫ73.1 in acetone) of 1c confirmed that absolute configuration of 1b is 2S and 3S.…”