Inhibitors of 4-hydroxyphenylpyruvate dioxygenase (HPPD) prevent plant carotenoid pigment formation, which in turn leads to chlorophyll degradation. This "bleaching" herbicide mode of action provides weed-control products for various crops, such as rice, corn, and cereals. Combinations with suitable safeners allow the full exploitation of the potential of this compound class to selectively control major weed problems, including rapidly increasing cases of resistance against other important herbicide classes.

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The deprotonation of a dicarbamate prepared from cis-1,2-cyclohexanedimethanol by sec-butyllithium/(À)-sparteine proceeds with efficient selection between the enantiotopic branches and their diastereotopic protons with high preference for the pro-S proton at the R branch to afford the intermediate, configurationally stable lithium compound as a single diastereomer. Trapping of this intermediate by electrophiles (DOMe, CO 2 , CH 3 I, Me 3 SiCl, or R 3 SnCl) takes place with retention of the configuration to yield highly enantiomerically and diastereomerically enriched substitution products, which are easily converted to diols, to anellated tetrahydrofurans, or to g-lactones. The chiral base is also capable of efficient kinetic resolution of the racemic adeuterated starting material, by the utilization of an extraordinarily high kinetic H/D isotope effect within the deprotonation step. The, presumably, first example of the kinetic resolution of a racemic stannane by lithiodestannylation, utilizing methyllithium/(À)-sparteine, is reported.

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HPPD‐Inhibitoren verhindern die Bildung der pflanzlichen Carotinoidpigmente, was wiederum zum Chlorophyllabbau führt. Dieser “Bleaching”‐Wirkmechanismus kommt bei Produkten zur Kontrolle von Schadpflanzen in unterschiedlichen Kulturen wie Reis, Mais und Getreide zum Einsatz. In Kombination mit einem geeigneten Safener lässt sich das Potential dieser Verbindungsklasse bei der selektiven Bekämpfung der wichtigsten Schadpflanzen, einschließlich der rasch zunehmenden Fälle von Resistenzen gegen andere wichtige Herbizidklassen, voll ausschöpfen.