comprehensive study of the basic components of Delphinium glaucescens, a toxic larkspur indigenous to the western United States, has led to the isolation of five new C19-diterpenoid alkaloids and nine known alkaloids. The known alkaloids, listed in order of decreasing abundance, are lycoctonine (16), dictyocarpine (2), browniine (9), 14-dehydrobrowniine (8), methyllycaconitine (12), delcosine (15), dictyocarpinine (7), deltaline (1), and anthranoyllycoctonine (17). Dictyocarpinine had not been isolated previously as a natural product. The structures of four of the new alkaloids, namely, glaucenine (3), glaucerine (4), glaucephine (5), and glaucedine (10), were firmly established by synthesis. Alkaloids 3, 4, and 10 contain ester groups which were previously unknown in the C19-diterpenoid alkaloids. The 2-methylbutyryl esters of 3 and 10 were determined to have the (S)-(+) configuration. The fifth new alkaloid, glaudelsine, was assigned structure 13 on the basis of its 13C NMR spectrum and the proton NMR spectrum of its hydrolysis product. © 1981, American Chemical Society. All rights reserved.