Kopsihainanines A and B, two unusual alkaloids from Kopsia hainanensis

Kopsihainanine A (1), an unprecedented skeleton with a 6/5/6/6/6 pentacyclic rearranged ring system, together with a new biogenetically related compound, kopsihainanine B (2), were isolated from Kopsia hainanensis. Their structures were elucidated by means of spectroscopic methods. The absolute configuration of 1 was determined by ECD calculation.