Steroid moiety

Na+/K+-ATPase. Figure 2 Specific Inhibitors of Na+/K+-ATPase. (a) Endogenous cardiac glycosides identified in mammals. Substances with a 5-membered lactone at position C17 of the steroid moiety are referred to as cardenolides, those with a 6-membered lactone as bufadienolides. (b) Palytoxin (C P NsO ) produced by corals of the genus Palythoa. 

Microwave-assisted Heck reactions have also been carried out with triflates as coupling partners, involving some very complex molecules. Winterfeld and coworkers have reported a multigram synthesis of a complex non-symmetrical bis-steroidal diene by microwave-promoted coupling of the corresponding alkene and triflate steroidal moieties (Scheme 6.8) [27]. 

Encouraged by the success of MUMBIs to synthesize biaryl ether macrocycles, we endeavored to combine this methodology with experience in steroid synthesis to obtain very large macrocycles with both peptide and steroid moieties (Fig. 21). These molecules bear no direct resemblance to any known natural products, but they do display a high degree of structural... 

Most cationic lipids are composed of either two lipophilic tails or a steroid moiety, typically based on cholesterol. The classic method for steroidyl incorporation involves the reaction of a steroidyloxycarbonyl halide (e.g. cholesteryloxycar-bonyl chloride (2)) with primary amines from the linking moiety, a method used for the synthesis of most cholesterol-based cationic lipids including DC-Chol (3) [68, 72] (Fig. 2b) and BGTC (7) [73] (Fig. 3a). 

Using the principle of ion pair formation between ammonium cations and the phosphate anions of lipids, Matile et al.33 prepared 8, an amphiphilic polyamine dendrimer. Rather than acting as a membrane channel, 8 was expected to form reversible membrane defects in the lipid bilayer. The steroid moiety was expected to act as the hydrophobic anchor for bilayer orientation and steric bulk was expected to prevent the polyamine penetrating the bilayer. Proton transport was assessed in unilamellar vesicles using the pH-fluorescence technique in which the external pH was increased to 7.8 relative to the internal pH at 7.4. The results demonstrated that 8 was almost as active as gramicidin, and maximal flux was achieved in ca. 20 s. 

A class of molecules (ALS) functionalized at C3 (which cannot be H-bond donors) are efficient gelators of many types of organic liquids. They consist of a group containing fused aromatic rings (A) connected to a steroidal moiety (S)... 

Bomah and co-workers [99] developed an efficient procedure for the synthesis of ring-A fused [3,2-h]pyrimidines 53 in a steroidal moiety. The novel steroidal pyrimidines were prepared via a solid phase three-component reaction of a 2-hydro-xymethylene-3-keto steroid, an arylaldehyde and ammonium acetate under micro-wave irradiation. This protocol has been applied successfully to the cyclization of bicyclic, monocyclic and acyclic 2-hydroxymethylene ketones with diversely substituted aromatic aldehydes (Scheme 39). 

A novel and versatile synthesis of dialkyl steroid phosphates employs the steroidal alkoxyl radical (545), generated by photolysis of the corresponding nitrite. In the presence of a trialkyl phosphite, the radical attacks at phosphorus to give a phosphoranyl radical (546), which loses one of its four alkyl groups to give the desired phosphate (547). The preference for expulsion of one of the small alkyl groups, rather than the steroidal moiety, is thought to be determined by... 

The synthesis of the steroidal moiety of batrachotoxin (459) has been attempted. In a first pilot-reaction sequence, 5/ 0,19N-[ep(oxyethano-N-methylimino)]-androstan-17-ol (461) was prepared from 17)5,19-diacetoxyandrost-4-en-3-one (460) by a multi-step sequence. The technique developed in this model synthesis was then applied to build the C(14)-C(18) ring of 3)5,20( -diacetoxy-14)50,18AT-[ep(oxyethano-N-methylimino)]-5a,17a-pregnane (463) from the pregnane intermediate (462). This experience was used in the synthesis of 3-0-methyl-17a,20( -tetrahydrobatrachotoxinin A (472) (see Schemes 37 and 38). ... 

Steroids such as estrogens, androgens and their derivatives have significant effects on the body and are implicated under various conditions including hormone replacement therapy. Most of the steroidal moieties have poor oral bioavailability due to high... 

B. Amino-glyco-steroids.—Partial syntheses of holantogenin (24) and anhydro-holantogenin (25), the steroidal moieties of the amino-glyco-steroids, holanto-sines A, B, C, and D,15 have been realised by two independent schools by similar... 

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