Stratingh Institute for Chemistry, Zernike Institute for Advanced Materials, and Center for Systems Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
J Org Chem. 2010 Feb 5;75(3):825-38. doi: 10.1021/jo902348u.
Controlling the unidirectional rotary process of second-generation molecular motors demands access to these motors in their enantiomerically pure form. In this paper, we describe an enantioselective route to three new second-generation light-driven molecular motors. Their synthesis starts with the preparation of an optically active alpha-methoxy-substituted upper-half ketone involving an enzymatic resolution. The subsequent conversion of this ketone to the corresponding hydrazone by treatment with hydrazine led to full racemization. However, conversion to a TBDMS-protected hydrazone by treatment with bis-TBDMS hydrazine, prepared according to a new procedure, proceeds with nearly full retention of the stereochemical integrity. Oxidation of the TBDMS-protected hydrazone and subsequent coupling to a lower-half thioketone followed by recrystallization provided the molecular motors with >99% ee. As these are the first molecular motors that have a methoxy substituent at the stereogenic center, the photochemical and thermal isomerization steps involved in the rotary cycle of one of these new molecules were studied in detail with various spectroscopic techniques.
控制第二代分子马达的单向旋转过程需要以其对映体纯的形式获得这些马达。在本文中，我们描述了三种新型第二代光驱动分子马达的对映选择性合成路线。它们的合成始于制备光学活性的α-甲氧基取代的上半酮，涉及酶促拆分。随后，用肼处理将该酮转化为相应的腙导致完全外消旋化。然而，用根据新程序制备的双 TBDMS 肼处理将其转化为 TBDMS 保护的腙，则几乎完全保留了立体化学完整性。TBDMS 保护的腙的氧化以及随后与下半部分硫代酮的偶联，再经过重结晶，为分子马达提供了 >99%的对映体过量。由于这些是在立体中心具有甲氧基取代基的第一个分子马达，因此详细研究了其中一种新分子的旋转循环中涉及的光化学和热异构化步骤，使用了各种光谱技术。
