Biogenetic type cyclization

A remarkable biogenetic type cyclization of Nerolidol to Cedrene was reported by Anderson et.al.,(Tet. Lett., 2455 (1972). The cyclizations could be accomplished in two steps. With formic acid a six membered ring is first formed. Further treatments with triflouroacetic acid completed the synthesis. The overall yield was very moderate (Figure 1.1).

Figure 1.1