Kishi’s-model

However, the stereochemistry of this osmylation would be opposite to Kishi s model which predicts an anti attack of the osmium tetroxide with respect to the 1-0R-function as shown by the conversion of 109 into 110. To circumvent this problem it was necessary to introduce the l-OR group first in the wrong configuration in order to... 

The issue of stereochemistry, on the other hand, is more ambiguous. A priori, an aldol condensation between compounds 3 and 4 could proceed with little or no selectivity for a particular aldol dia-stereoisomer. For the desired C-7 epimer (compound 2) to be produced preferentially, the crucial aldol condensation between compounds 3 and 4 would have to exhibit Cram-Felkin-Anh selectivity22 23 (see 3 + 4 - 2, Scheme 9). In light of observations made during the course of Kishi s lasalocid A synthesis,12 there was good reason to believe that the preferred stereochemical course for the projected aldol reaction between intermediates 3 and 4 would be consistent with a Cram-Felkin-Anh model. Thus, on the basis of the lasalocid A precedent, it was anticipated that compound 2 would emerge as the major product from an aldol coupling of intermediates 3 and 4. 

The structures of PMs are trimeric, consisting of three molecules of PS and two molecules of methylamine that are condensed together (Table 9.5). In the structures of PMs, however, the bonds created by the condensation lack adjacent hydrogen atoms, making the connectivity assignment in 1H-NMR studies virtually impossible (see the 9-membered rings in Fig. 9.11). To circumvent this problem, a model compound of panal, K-l, having 13C-labeles at the C12 and C13 positions, has been synthesized at Kishi s laboratory (Harvard University) to make a model compound of PM (Stojanovic, 1995). 

Morizane R, Lam AQ, Freedman BS, Kishi S, Valerius MT, Bonventre JV. 2015. Nephron organoids derived from human pluripotent stem cells model kidney development and injury. Nat Biotechnol 33(11) 1193-1200. 

The extremely high sensitivity of bacteriochlorins to various reactions makes their chemistry very difficult. This might also be one reason why methods for the total synthesis of bacteriochlorins had not, until very recently, been developed.13 Total synthesis of a tolyporphin model was reported by Kishi et al.13 using an approach that is very closely related to Eschenmoser s syntheses of hexahydroporphyrins from reduced linear tetrapyrroles by cyclization (see Section 1.5.1). 

Takagi Y, Takahashi J, Saiki H, Morizane A, Hayashi T, Kishi Y, Fukuda H, Okamoto Y, Koyanagi M, Ideguchi M, Hayashi H, Imazato T, Kawasaki H, Suemori H, Omachi S, lida H, Itoh N, Nakatsuji N, Sasai Y, Hashimoto N (2005) Dopaminergic neurons generated fiom monkey embryonic stem cells function in a Parkinson primate model. J Clin Invest 115 102—109. 

---