Scheme 4. Ring expansion to polycyclic scaffolds. Conditions: a (1) KHMDS (2 equiv.), THF, 0 °C, 1–1.5 h; (2) MeOH. ^aAccompanied by products of urea cleavage. ^bA lactam resulting from oxidation of 10 was isolated in 26% yield. CCDC deposition numbers for X-day data: 11a1993730; 11f1993731; 11g1993732.†.