methyl 15,16-dihydro-15,16-dihydroxyisopimarate   、                                                                                      
丙酮                                                                                                                                                              在
                                                                                                                                                                                 
copper(II) sulfate                                                                                                                                  作用下,
                                                                                                                                                                                        反应 16.0h,
                                                                                                                以75%的产率得到(1R,4aR,4bS,7S,10aR)-7-(2,2-Dimethyl-[1,3]dioxolan-4-yl)-1,4a,7-trimethyl-1,2,3,4,4a,4b,5,6,7,8,10,10a-dodecahydro-phenanthrene-1-carboxylic acid methyl ester