Germanes chiral, synthesis

In a report describing the first enzymatic synthesis of a chiral nonracemic tetraorgano germane, Tacke and coworkers subjected the prochiral cis-hydroxymethyl derivative (10) to acetylation catalyzed by pig liver esterase (Scheme 3)6. The resulting monoacetate (11) was shown to be of 55% ee through 11 NMR analysis of the Mosher ester derivative. 

A. S. Bommarius, Development of enzymatic process for the synthesis of chiral building blocks with emphasis on protein stability (in German), Habitation thesis, RWTH Aachen, Aachen, Germany, 2000. 

Halogermane reductions by complex hydrides are efficient, preferred methods for germane synthesis " . The complex hydrides used are MBH (M = Li, Na, K) and LiAlH.,. Reduction of Ge—X bonds by this method can be used for any molecule that otherwise is unsusceptible to complex hydride reduction or reaction. Lithium tetrahydroaluminate reduction of chiral halogermanes and alkoxygermanes results in inversion and retention of configuration, respectively. The LiBH., and LiAlH reactions require aprotic solvents, such as EtjO, THF, n-Bu O or glyme ethers. Sodium and K... 

Gandolfi, C., Pellegata, R., Ceserani. R.. and Usardi, M.M., co-iVor-cycloalkyl-13,14-dehydroprostaglan-dins, Farmitalia Carlo Erba, German Patent Appl. DE 2539116, 1976 Chem. Abstr, 85, 77748, 1976. Braun, N.A., Klein, I., Spitzner. D.. Vogler, B., Braun, S., Borrmann, H., and Simon, A., Cascade reactions with chiral Michael acceptors. Synthesis of enantiomerically pure tricyclo[3.2.1.0 - ]- and bicyclo[3.2.1]octanes, Liebigs Ann. Org. Bioorg. Chem., 2165, 1995. 

The diversity of ordered porous solids increases at an astonishing rate, particularly among the readily crystallised MOFs, and continues to olfer novel materials properties. There is no obvious barrier to the synthesis of a myriad of new zeolite, zeotype or hybrid structures. Challenges remain, however. For zeolitic aluminosilicates, the 10 A pore size restriction remains an important barrier, and an enantiomerically pure zeolite is still out of reach. For nonsilicate crystalline microporous solids, thermal and hydrothermal stability, rather than framework geometry, limit their applicability, since fully crystalline germanates and carboxylates with pores in the mesoporous range now exist, and these solids have enormous specific surface areas. In these hybrid solids the ability to choose chirality in the building units indicates that it will be possible to prepare these in chiral form the first examples have already been prepared. 

The first report of an asymmetric hydrogenation catalyst refers to a German Patent (Bursian and Pracejus, 1972) where a rhodium complex with phosphinated cellulose was used. In two recent reports, an elaborate synthesis of a rhodium complex of a polymer having a chiral phosphine... 

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