TWO new spirobenzylisoquinoline alkaloids obtained from Pakistani Corydalis stewartii are (+)-ochotensidine [1] and (+)-corystewartine [4]. The stereochemistry of the known (+)-raddeammine [5] is identical to that of 4. Some 320 Corydalis plant species, belonging to the family Fumariaceae, have been recognized. They occur mostly in the northern hemisphere, particularly in the temperate and tropical zones of Asia. Among these species, 71 have been studied to some extent, and all have been found to produce isoquinoline alkaloids (1). Corydalis stewartii Fedde grows in the mountainous regions of Pakistan. Initial studies indicated the presence of the aporphines (+)-isoboldine and (+)-domesticine, the protoberberines (+)-tetrahydrocoptisine and coptisine, and also the ketonic base protopine which is always present in Corydalis species (2-4). Presently, a reinvestigation of C. stewartii, collected in Pakistan, afforded, besides the known phthalideisoquinoline (+)-adlumidine and the aporphine (+)-domesticine, four spirobenzylisoquinolines, namely (+)-ochotensidine [1], (+)-ochotensine [2], (+)-ochotensimine [3], and (+)-corystewartine [4]. Of these four, compounds 1 and 4 are new. Because previous nmr spectral data for compounds 2 and 3 were limited or unavailable (5), our initial endeavor was to carry out a detailed analysis of the nmr spectrum of (+)-ochotensimine [3]. The spectral results are given around expression 3. Significantly, the vinylic proton absorbing at δ 5.64 showed an nOe with H-12 (δ 7.11), while the vinylic proton at δ 4.90 displayed an nOe with H-6α (δ 2.96) and with H-1 (δ 6.29). It was also possible to differentiate between the two C-8 protons. H-8β (δ 2.96) exhibited reciprocating nOe's with H-1 (δ 6.29), whereas the N-methyl singlet (δ 2.15) showed an nOe with H-8α (δ 3.45). The chemical shifts in the nmr spectrum of (+)-ochotensine [2] were then assigned by analogy with those of alkaloid 3. The nmr spectrum of the new alkaloid (+)-ochotensidine [1] was clearly related to those for analogues 2 and 3. The main difference was the presence of a methylenedioxy substituent on ring A in lieu of the two methoxyls of (+)-ochotensimine [3]. It should be noted that in the spectrum of 1, the methylenedioxy protons on ring A absorb at higher field than those on ring D. The mass spectrum of (+)-ochotensidine [1] presented molecular ion m/z 349 which was also the base peak. Loss of a methyl group then supplied the significant [M - 15]+ ion, m/z 334. Our second new spirobenzylisoquinoline, (+)-corystewartine [4], C₂₀H₂₁NO₅, was different from the preceding three alkaloids in that its nmr spectrum was devoid of vinylic absorptions. Instead, a C-methyl singlet was in evidence at δ 1.26. The complete nmr spectral information is presented around expression 4. Two methylenedioxy groups are clearly observable, with the one attached to ring D absorbing further downfield. The mass spectrum of (+)-corystewartine [4] included small molecular ion m/z 367 (3%). An important peak was m/z 352 (64%) formed mostly by loss of the 13-Me group. Alternatively, loss of H₂O from the molecular ion produced ion m/z 349 (9%). Base peak m/z 190 is due to rings A and B. Attempted acetylation of (+)-corystewartine [4] using Ac₂O in pyridine furnished instead (+)-ochotensidine [1], thus directly interrelating the two new alkaloids. An nmr nOe study was carried out on (+)-corystewartine [4] specifically for the purpose of establishing the relative stereochemistry at C-13. Reciprocating nOe's were observed between H-1 (δ 6.21) and the 13-Me singlet (δ 1.26), indicating that the methyl group lies syn to ring A. It should be noted that the known spirobenzylisoquinoline alkaloid (+)-raddeanamine [5], which also bears methyl and hydroxyl substituents at C-13, shows an nmr spectrum with a 13-Me singlet at δ 1.23 (6,7). This value compares very well with the corresponding value for (+)-corystewartine [4], δ 1.26, so that raddeanamine must have the identical stereochemistry at C-13. It is also known that dextrorotatory spirobenzylisoquinolines such as ochotensine [2] exhibit in their cd spectra a positive Cotton effect centered around 280 nm (8). (+)-Ochotensidine [1] also presents a similar cd pattern (see Experimental section), which indicates that compounds 2 and 4 incorporate the identical chirality. The absolute configuration of (+)-corystewartine [4] is settled by its ready conversion into (+)-ochotensidine [1].