Synthesis of Monodisperse Macromolecular Bicyclic and dendritic compounds from (R)‐3‐hydroxybutanoic acid and benzene‐1,3,5‐tricarboxylic acid and analysis by fragmenting MALDI‐TOF mass spectroscopy

Abstract

Dedicated to Professor Waldemur Adam on the occasion of his 60th birthday(1 1 N.97)As previously shown, oligo-and poly(p-hydroxyalkanoates) have a high tendency to form lamellar crystallites with ca. 50-8, thickness which corresponds to chain lengths of 16 units (Fig. f). To have monodisperse model compounds, we have now prepared bicyclic derivatives with three parallel (27-29) or two parallel and an antiparallel chain (68-70) consisting of up to 16 3-hydroxybutanoate (3-HB) units. We also prepared dendritic compounds (71 -75,82-85) containing oligo(3-HB) chains which cannot possibly be arranged as in the lamellue; the branching units were prepared from trimesic acid (= benzene-l,3,5-tricarboxylic acid). So far, none of the prepared samples formed crystals or contained crystalline domains which would have been suitable for single-crystal or powder-diffraction X-ray analysis. The terminally deprotected dendrimers (74,75, and 85) are multi-anionic (up to 12 peripheral CO,H groups) and biodegradable. The macromolecular HB derivatives (molecular weight up to 10150 Da) have been fully characterized by IR, 'H-and I3C-NMR, [a],, and elemental analysis. Especially important is the analysis by mass spectrometry with the MALDI-TOF technique (Fig. 2), proving that the products are monodisperse; application of a new variation of this MS method (post source decay = PSD or fragment analysis by structural rime of flight = FASTTM) allows for the observation of metastable fragment ions and, thus, is a tool for structural oligomer analysis (Fig. 3). 1. Introduction. -Poly(P-hydroxyalkanoates) (PHAs), an ubiquitous class of biopolymers [2] have been the subject of research in our group for many years [3]. Besides their occurrence as a high-molecular-weight storage material (sPHA) in microorganisms [4] PHAs have also been found in a low-molecular-weight form (cPHA). Reusch and coworkers have shown that low-molecular-weight poly[(R)-3-hydroxybutanoic acid] (P(3-HB) = PHB), ca. 150 units) and CaPP, (calcium polyphosphate) form a complex which may function as an ion channel in genetically competent E. coZi cells [5] [6]. P(3-HB) has also been detected in eucaryotic cells, in human aorta tissue [6], and in blood plasma [5b]. From most of these sources, cPHB and its homolog cPHV (V = valerate = pentanoate) could be extracted with CHC1, and characterized by NMR spectroscopy [6]. Most recently, however, much larger quantities of PHB and PHV have been detected (by degradation to crotonic acid (= but-2-enoic acid) at higher temperature and/or larger reaction times [7], or by transesterifying conversion to ethyl (R)-3-

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A comparison of X-ray crystal structures including methyl 3,5-bis(hydroxymethyl)benzoate, its phenylethynyl extended derivative in polymorphous forms and the corresponding carboxylic acids

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Fragmentation study of rutin, a naturally occurring flavone glycoside cationized with different alkali metal ions, using post‐source decay matrix‐assisted laser desorption/ionization mass spectrometry

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