4-(4-methoxybenzyl)-4-methyltetrahydro-2H-pyran-3-carboxylic acid                                                                                                                                                              在
                                                                                                                                                                                 polyphosphoric acid                                                                                                                                  作用下,
                                                                                                                                                                                        反应 0.67h,
                                                                                                                生成                                                 8-methoxy-4a-methyl-3,4,4a,5-tetrahydro-1H-benzo[g]isochromen-10(10aH)-one   、                                                                                             cis-8-methoxy-4a-methyl-3,4,4a,5-tetrahydro-1H-benzo[g]isochromen-10(10aH)-one