4',9'-dihydro-N,N-dimethyl-4-cyclopentyl-spiro[cyclohexane-1,1'(3'H)-pyrano[3,4-b]indol]-4-amine   、                                                                                      
柠檬酸                                                                                                                                                                                              以
                                                                                         
乙醇                                                                                  为溶剂,
                                                                                                                                                                                        以50%的产率得到4',9'-dihydro-N,N-dimethyl-4-cyclopentyl-spiro[cyclohexane-1,1'(3'H)-pyrano[3,4-b]indol]-4-amine hemi(2-hydroxy-1,2,3-propanetricarboxylate)