Multistep synthetic routes to eight structurally diverse and medicinally relevant targets were planned autonomously by the Chematica computer program, which combines expert chemical knowledge with network-search and artificialintelligence algorithms. All of the proposed syntheses were successfully executed in the laboratory and offer substantial yield improvements and cost savings over previous approaches or provide the first documented route to a given target. These results provide the long-awaited validation of a computer program in practically relevant synthetic design.

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Highly chromogenic 18-crown-6-dipyrrolylquinoxaline coordinates primary amines of peptides, forming non-covalent complexes that can be transferred to the gas-phase by electrospray ionization. The appended chromogenic crown ether facilitates efficient energy transfer to the peptide upon ultraviolet irradiation in the gas phase, resulting in diagnostic peptide fragmentation. Collisional-activated dissociation and infrared multiphoton dissociation of these non-covalent complexes result only in their disassembly with the charge retained on either the peptide or crown ether, yielding no sequence ions. Upon UV photon absorption the intermolecular energy transfer is facilitated by the fast activation timescale of ultraviolet photodissociation (Ͻ10 ns) and by the collectively strong hydrogen bonding between the crown ether and peptide, thus allowing effective transfer of energy to the peptide moiety before disruption of the intermolecular hydrogen bonds. T he ongoing need for improved methods for characterizing biological molecules is driving efforts to develop new ion activation and dissociation approaches in mass spectrometry (MS) [1,2]. Currently, collisional-activated dissociation (CAD) remains the most popular technique used to produce diagnostic fragment ions [3,4]. However, this MS/MS method is subject to a number of shortcomings such as insufficient or inefficient energy deposition. Accordingly, a number of other techniques, including surface induced dissociation (SID) [5], electron capture dissociation (ECD) [6,7], electron-transfer dissociation (ETD) [8], and photodissociation (PD) [9 -22] have been developed in recent years. Of these, photodissociation appears particularly attractive because it offers the possibility of tuning the level of energy deposition and providing high-energy input without collisional scattering effects; it is also compatible with both time-of-flight and ion trapping platforms [9 -22]. Unfortunately, as currently practiced, photodissociation requires that the ions of interest absorb the specific wavelength to induce fragmentation. This is often problematic because many biological molecules display regions of low absorptivity over much of the UV/Vis spectral range. To overcome this deficiency, efforts have been made to append external chromophores to molecules of interest, and this is an approach that we [23,24] and others are exploring [25]. However, far more appealing and potentially more general is the idea of attaching chromophores via non-covalent interactions as an attractive alternative because of its simplicity and potential versatility. On the other hand, non-covalent interactions are relatively weak. This makes it a challenge to design chromogenic receptors that not only can bind to various target ions of interest but also can allow energy transfer following photoexcitation. In this report we describe a simple first-generation chromogenic molecule (18-crown-6-dipyrrolylquinoxaline, 1) [26] that binds non-covalently to peptides via hydrogen bonding interactions and allows effe...

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The synthesis, characterisation and properties of an artificial ion channel containing a redox-active ferrocene unit are described.