Highly Regioselective Diels−Alder Reactions toward Oroidin Alkaloids:  Use of a Tosylvinyl Moiety as a Nitrogen Masking Group with Adjustable Electronics

• Published in: Organic letters Vol. 7; no. 9; pp. 1679 - 1682
• Main Authors: Dransfield, Paul J, Wang, Shaohui, Dilley, Anja, Romo, Daniel
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 28.04.2005; Amer Chemical Soc
• Subjects: Alkaloids - chemistry; Amines - chemical synthesis; Chemistry; Chemistry, Organic; Molecular Structure; Physical Sciences; Pyrroles - chemistry; Science & Technology; Spiro Compounds - chemistry; Stereoisomerism; Tosyl Compounds - chemistry; Vinyl Compounds - chemistry; PALAUAMINE; CORE; SPONGE AXINELLA SP; 4-VINYLIMIDAZOLES; STRATEGY; PYRROLE-IMIDAZOLE ALKALOIDS
• ISSN: 1523-7060; 1523-7052
• DOI: 10.1021/ol0473602

The use of the p-toluenesulfonyl (Ts) and tosylvinyl (Tsv) groups as nitrogen masking groups imparted high regioselectivity in Diels−Alder reactions directed toward members of the oroidin-derived marine alkaloid family. The electron-withdrawing Tsv group was utilized as an electronically adjustable nitrogen-protecting group as subsequent hydrogenation provided the more electron-rich tosylethyl (Tse) group. This electronic adjustment strategy avoided a protecting group exchange and provided the required electronics for the key chlorination/ring-contraction sequence.