Photogeneration of amines from α-keto carbamates: design and preparation of photoactive compounds
作者:James F. Cameron、C. Grant Willson、Jean M. J. Fréchet
DOI:10.1039/a602018f
日期:——
The design and synthesis of substituted desyl
(2-oxo-1,2-diphenylethyl) groups has been investigated to create new
photolabile protecting groups. The photoreactivity of these chromophores
stems from the diverse photochemistry of the desyl group. Several
chromophore designs have been explored in which the substitution pattern
of the parent desyl chromophore was varied systematically. The required
benzoin chromophores are prepared by a variety of synthetic routes,
depending on the structure of the benzoin chromophore desired.
Symmetrical benzoins are readily available via the benzoin
condensation. Unsymmetrical benzoins including 2,2-disubstituted
α-hydroxy ketones are generally prepared via
trimethylsilyl (TMS) masked cyanohydrins. On reaction with a Grignard
reagent, the TMS masked cyanohydrin functions as an
α-hydroxycarbonyl equivalent to form
α-hydroxy ketones. Alternatively, lithiation of a TMS
masked cyanohydrin generates a benzoyl anion equivalent which reacts
with aldehydes and ketones to generate substituted benzoins. These desyl
chromophores have significant potential as new photolabile protecting
moieties for a variety of functional groups and are used to mask primary
and secondary amines as photosensitive α-keto carbamates.
The substituted benzoin carbamates are readily prepared from the
appropriate benzoin by reaction with isocyanates or by activation as a
mixed carbonate followed by reaction with the free amine. These
α-keto carbamates are interesting for two main reasons.
First, the facile synthesis of these materials indicates the ease of
introduction of the desyl based photolabile group. Second, these
α-keto carbamates may be used for rapid evaluation of
novel photoactive desyl based chromophores.
对取代的德亚尔(2-氧-1,2-二苯乙基)基团的设计和合成进行了研究,以创建新的光敏保护基团。这些颜料的光反应性源于德亚尔基团的多样光化学。已经探索了几种颜料设计,其中母体德亚尔颜料的取代模式被系统地变化。所需的苯基醇颜料通过多种合成途径制备,这取决于所需苯基醇颜料的结构。对称的苯基醇可以通过苯基醇缩合法轻松获得。包括2,2-二取代的α-羟基酮在内的不对称苯基醇通常通过三甲基硅基(TMS)掩蔽氰醇生成。与格氏试剂反应时,TMS掩蔽氰醇作为α-羟基羰基等价物,形成α-羟基酮。或者,TMS掩蔽氰醇的锂化生成苯甲酰阴离子等价物,与醛和酮反应生成取代苯基醇。这些德亚尔颜料作为新型光敏保护基团在多种功能基团中具有重要潜力,被用于掩蔽一级和二级胺,作为光敏α-酮氨基甲酸酯。取代的苯基醇氨基甲酸酯可以通过与异氰酸酯反应,或通过作为混合碳酸盐活化后与游离胺反应,从适当的苯基醇中容易制备。这些α-酮氨基甲酸酯在两个主要方面颇具趣味。首先,这些材料的简单合成表明引入德亚尔基光敏基团的容易性。其次,这些α-酮氨基甲酸酯可用于快速评估新型光活性德亚尔基颜料。