Cyclic peptides have been attracting a lot of attention in recent decades, especially in the area of drug discovery, as more and more naturally occurring cyclic peptides with diverse biological activities have been discovered. Chemical synthesis of cyclic peptides is essential when studying their structure−activity relationships. Conventional peptide cyclization methods via direct coupling have inherent limitations, like the susceptibility to epimerization at the C-terminus, poor solubility of fully protected peptide precursors, and low yield caused by oligomerization. In this regard, chemoselective ligation-mediated cyclization methods have emerged as effective strategies for cyclic peptide synthesis. The toolbox for cyclic peptide synthesis has been expanded substantially in the past two decades, allowing more efficient synthesis of cyclic peptides with various scaffolds and modifications. This Review will explore different chemoselective ligation technologies used for cyclic peptide synthesis that generate both native and unnatural peptide linkages. The practical issues and limitations of different methods will be discussed. The advance in cyclic peptide synthesis will benefit the biological and medicinal study of cyclic peptides, an important class of macrocycles with potentials in numerous fields, notably in therapeutics. CONTENTS

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Since Fleming’s discovery of penicillin nearly a century ago, a bounty of natural product antibiotics have been discovered, many of which continue to be of clinical importance today. The structural...

The development of the first enantioselective para-Claisen rearrangement has been achieved. Using a chiral aluminum Lewis acid, illicinole is rearranged to give (−)-illicinone A (er 87:13), which can then be converted into more complex Illicium-derived prenylated phenylpropanoids. The absolute configurations of the natural products (+)-cycloillicinone and (−)-illicarborene A have been determined, and our results cast doubt on the enantiopurity of the natural samples.