Synthesis of boron dipyrromethene fluorescent probes for bioorthogonal labeling

Seven 5-substituted 3-hydrazinyl derivatives of 3a, 4a-diaza-4,4-difluoro-8-phenyl boron dipyrromethene (BODIPY) were prepared for use as bioorthogonal fluorescent labels of aldehydes and ketones. The absorption energies can be tuned to absorb visible light over a large span of wavelengths by changing the nature of the 5-substituent. Optical properties of hydrazones formed with the 5-chloro derivative are affected by the nature of the electrophile such that aliphatic and aromatic hydrazones can be differentiated from each other and from unreacted fluorophore.

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