Steroids hydrogen bonding

While the foregoing concepts have been utilized to rationalize the product distribution obtained on hydrogenation of a number of monocyclic olefins, it should be noted that the effect of pressure on the stereochemistry of hydrogenation of steroidal double bonds has not been critically evaluated. 

In general the rates of hydrogenation of steroidal double bonds can be roughly classified as follows a) readily hydrogenated A, A, A", A , A14 A diene, A , A ° and 19-vinyl (Z>) moderately difficult ... 

Abraham, M. H. Martins, F. Mitchell, R. C., Algorithms for skin permeability using hydrogen bond descriptors The problems of steroids, J. Pharm. Pharmacol. 49, 858-865 (1997). 

The cage-type peptide cyclophanes (7 and 8) exhibit discrimination toward steroid hormones, as effected by hydrophobic and n-n interactions. In addition, the chirality-based discrimination between a- and -estradiol as well as between D- and L-amino acids bearing an aromatic moiety is performed on the basis of their capacity of forming efficient hydrogen bonding with the host molecules in aqueous media [41, 43]. 

Figure 6d shows the modeled a helix F interface in pig 17 P-hydroxy steroid dehydrogenase type 4. Leucine-169 is 2.9 A from glycine-173. Leucine-174 is 4.3 A from alanine-162 and 3.3 A from alanine-166. There also is a hydrogen bond between serine-165 and serine-175, which are 3 A apart. 

Raney nickel, 119, 132, 134, 135, 138 Rates of hydrogenation of steroidal double bonds, 119... 

In general the rates of hydrogenation of steroidal double bonds can be roughly classified as follows (a) readily hydrogenated A1, A2, A3, A4, A6, A14, A15 A14 16 diene, A16, A17(20), A20 and 19-vinyl (b) moderately difficult A5 > A22 and (c) difficult to hydrogenate A8 > A9(11) > A7 > A8(14). The data for the hydrogenation of A7-steroids is obscurred by the fact that this olefin is isomerized readily to the 8(14) position. Double bond isomerization does not occur with A7-9/ -steroids.18,23,39,54... 

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