Biotin (1), a water-soluble B series vitamin, distributes widely in microorganisms, plants, and animals. Biosynthesis of 1 involves five steps sequence starting from pimelic acid. The last step, a transformation from dethiobiotin (DTB) to 1, includes an iron clusters-mediated radical process. The compound 1 is a cofactor of carboxylation enzymes and plays crucial roles in the metabolism of fatty acids, sugars, and alpha-amino acids. In addition to the increasing application to feed additives, recent reports have revealed that 1 enhances insulin secretion in animals, suggesting it for a promising therapeutic candidate for an anti-diabetes drug. The remarkably strong affinity of 1 with avidin and streptavidin has been extensively applied for such technologies as photoaffinity labeling. Among the number of approaches to 1 so far developed in 50 years, a synthesis using L-cysteine and thiolactone as a starting material and a key intermediate, respectively, represents one of the best routes leading to 1, because of short steps, high yield, use of inexpensive reagents, and ease of operation. Copyright 2006 Wiley Periodicals, Inc.