Joachim Dr. Paust

A Short and Productive Synthesis of Racemic α-Lipoic Acid

(R )-α-Lipoic acid is synthesized in seven steps from the base chemicals methyl acetoacetate or Meldrum’s acid and monomethyl adipate. The key steps are the introduction of the stereogenic center by fermentative or homogeneously catalyzed hydrogenation of 3-oxooctanedioic acid diester to (3S)-3-hydroxyoctanedioic acid diester and its regioselective reduction to (6S)-6 ,8-dihydroxyoctanoic acid ester. The overall yield of (R )-α-lipoic acid, starting from 3-oxooctanedioic acid diester, is 40%.

Nonlinear optics of astaxanthin thin films

Carotinoids exhibit large nonlinear optical properties due to their extended (pi) -electron system. Compared to other polyenes which show a broad distribution of conjugation lengths, carotinoids exhibit a well defined molecular structure, i.e. a well defined conjugation length. Therefore the carotinoid molecules can serve as model compounds to study the relationship between structure and nonlinear optical properties. In this paper the synthesis of four astaxanthins with C-numbers ranging from 30 to 60, their preparation into thin films, wavelength dispersive Third Harmonic Generation (THG) measurements and some molecular modelling calculations will be presented. Resonant (chi) (3) values reach 1.2(DOT)10-10 esu for C60 astaxanthin. In the nonresonant regime a figure of merit (chi) (3)/(alpha) of several 10-13 esu-cm is demonstrated.