Methylated crystallographic studies

Tile data on H- and C-cliemical shifts, H-relaxation rates, and protonation for 2-arylimidazo[l,2- ]imidazoles (107) and their methyl derivatives 108 and 109 indicate that 107 exists predominantly as the 1/7 tautomer 107a in CDCI3 and as the IH tautomer 107b in DMSO-dg or CD3OD-D2O (91MRC1147). An X-ray crystallographic study has demonstrated the IH tautomer 107a in the lattice. 

The first cyclopentadienylzinc compound that was structurally characterized by an X-ray crystallographic study is cyclopentadienyl(methyl)zinc, Cp(Me)Zn (57) ". The structure of 57 in the solid state consists of puckered chains of methylzinc fragments, linked by bridging cyclopentadienyl groups (Figure 28). 

Reaction of two equivalents of 2-[(dimethylamino)methyl]ferrocenyUithium with ZnCl2 affords the corresponding diorganozinc compound (68) in which two 2-[(dimethylamino) methyl]ferrocenyl ligands are C,Af-chelate bonded to zinc. Due to the chirality of the bidentate ligands 68 exists in two diastereoisomeric forms. Indeed, in solution a meso one and an S,S)/ R,R) enantiomeric parr in a 1 4 ratio were observed by H and C NMR spectroscopy. However, it is only the S,S)/ R,R) enantiomeric pair that preferentially crystallizes from solution. An X-ray crystallographic study of such crystals afforded the structure of (R,R)/(S,S)-6S in the solid state (Figure 35). 

The cyano complex [Au(CN)fCNMe)] has been prepared by treating [Au(CN)2] with methyl iodide (136), and its near-linear structure was elucidated from X-ray crystallographic studies. 

By crystallization of a mixture of the dipeptide (2) and racemic methyl lactate from methanol, asymmetric recognition occurred to give an inclusion compound that contains the (S)-form of methyl lactate in 89 % ee [20], X-ray crystallographic study of the inclusion compound was able to elucidate that the dipeptide molecules... 

Of seven structurally known daphniphylline-type alkaloids, the structure of daphniphylline (1) was first elucidated by an X-ray crystallographic analysis of the corresponding hydrobromide (4). Further X-ray crystallographic studies on daphmacrine methiodide revealed it to have the absolute configuration depicted as 18 (5). Methyl homosecodaphniphyllate (29) has also been proved to have the same absolute configuration as that of daphmacrine (6). Therefore, the... 

The structure of autumnaline has been confirmed by an X-ray crystallographic study of 3-methyl-7-0-benzylautumnaline (30).41 Autumnaline itself has been isolated from Colchicum latifolium.42... 

The structures of anopterine (73) and its hydrolysis product, anopteryl alcohol (74), had previously been assigned on the basis of an X-ray crystallographic study of the azomethine iodide (75) formed on treatment of tetra-acetylanopteryl alcohol (76) with methyl iodide. The structure of the original alkaloid was derived from this azomethine by an n.m.r. study43 (c/. Vol. 4, p. 325). 

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