Comprehensive Summary Five new pyrrolizidine alkaloids, bohemamines J-N (1-5), were isolated from Streptomyces sp. CPCC 200497. Their structures were assigned based on detailed spectroscopic analysis and semisynthesis. Bohemamine J (1) possesses a new chimeric skeleton derived from bohemamine A (6) and phenylacetaldehyde. Inspired by the nonenzymatic formation mechanism of the methylene-bridged dimers isolated from this strain, we synthesized a series of chimeric derivatives (8, 9, and 12-23) through natural product chimera strategy. Compounds 13, 15, 19, and 21 showed significant antioxidant activity.