Reductive amination of methyl 16-formyllambertianate with tryptamine, followed by Pictet-Spengler cyclization of the resulting diterpenoindole amine with formaldehyde, yields methyl 16-(1,2,3,4-tetrahydro-beta-carbolin-2-ylmethyl)lambertianate. The reaction of formyl-substituted methyl labdatrienoates and labdadienoates with 2-(3-indolyl)ethylamines provides a convenient approach to 1-diterpeno-beta-carbolines.