Scheme 3 Synthesis of 1 via a Weinreb amide here shown with the modifications of the Taylor group. 17Scheme 4 1 and 8 as precursors for the and -2-aminohydroxypropyl structural element.
Functionalized compounds, which are difficult to produce by classical chemical synthesis, are of special interest as biotechnologically available targets. They represent useful building blocks for subsequent organic syntheses, wherein they can undergo stereoselective or regioselective reactions. "White Biotechnology" (as defined by the European Chemical Industry [ http://www.europabio.org/white_biotech.htm ], as part of a sustainable "Green Chemistry,") supports new applications of chemicals produced via biotechnology. Environmental aspects of this interdisciplinary combination include: Use of renewable feedstock Optimization of biotechnological processes by means of: New "high performance" microorganisms On-line measurement of substrates and products in bioreactors Alternative product isolation, resulting in higher yields, and lower energy demand In this overview we describe biotechnologically produced pyruvic, 2-oxopentaric and 2-oxohexaric acids as promising new building blocks for synthetic chemistry. In the first part, the microbial formation of 2-oxocarboxylic acids (2-OCAs) in general, and optimization of the fermentation steps required to form pyruvic acid, 2-oxoglutaric acid, and 2-oxo-D-gluconic acid are described, highlighting the fundamental advantages in comparison to chemical syntheses. In the second part, a set of chemical formula schemes demonstrate that 2-OCAs are applicable as building blocks in the chemical synthesis of, e.g., hydrophilic triazines, spiro-connected heterocycles, benzotriazines, and pyranoic amino acids. Finally, some perspectives are discussed.
Starting from D-arabinose the synthesis of the very strong glycosidase inhibitors isofagomine (2) and noeuromycin (3) was achieved in six and seven steps, respectively. Keystep in the reaction sequence is the application of an efficient C-4 oxidation method to benzyl alpha-D-arabino-pyranoside. Subsequent Henry reaction of the obtained aldoketose with nitromethane provided the required branched carbohydrate precursors, which gave access to 2 and 3 in 17-21% overall yield.
The presented extended release pellet formulation is able to maintain a low pH within the pellet core and thus a sufficiently high drug solubility. By maintaining a low pH inside the pellets, a controlled drug release can be achieved.
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