## 3 Application of Complex [PtH{(PMe2O)2H}(PMe2 OH)] in the Total Synthesis of Natural Products
The same group also described the synthesis of different psycherin analogues from primary amide **44**, which was also accessed though a nitrile hydration reaction promoted by **1**[56, 57]. The total syntheses of the prenylated indole alkaloids citrinalin B (**47**) and cyclopiamine (**48**) has been recently accomplished for the first time by [PERSON], [PERSON], and co-workers (Scheme 12) [60]. In their work, the key carbamate intermediate **46** was generated through a two-step sequence from tricyclic nitrile **45** via initial hydration of the C\(\equiv\)N catalyzed by complex [PtH{(PMeO)2H}(PMe2 OH)] **(1)**, followed by Hofmann rearrangement of the resulting carboxamide (not isolated) promoted by PIFA in MeOH. Figure 3: Structure of psycherin and amides **43–44**. **Scheme 12. ** The Parkins catalyst in the total synthesis of citrinalin B and cyclopiamine B. In an independent work, [PERSON] and co-workers reported the preparation of the related 17-hydroxy-citrinalin B (**50**), as well as those of the alkaloids stephacidin A (**51**) and notoamide I (**52**), using carbamate **49** as a common intermediate (Figure 4) [61]. As in the previous case, formation of **49** was accomplished through a hydration/Hofmann rearrangement sequence from the corresponding nitrile, the hydration step being again promoted by the Parkins platinum catalyst **1**. Finally, [PERSON] and co-workers reported the preparation of a series of morinol-type lignans **55** starting from \(\alpha\),\(\beta\)-unsaturated nitriles **53** (Scheme 13) [62]. The selective transformation of the alkenenitrile unit of **53** into the allylic alcohol one involved an initial hydration step, catalyzed by complex [PtH{(PMe2O)2H}(PMe2 OH)] (**1**), followed by an acylation/reductio  
Figure 4: Structure of the carbamate **49** and the alkaloids **50–52**. Application of Complex [PtH{((PMe2O)2H)(PMe2 OH)] in the Synthesis of Other Biologically Active Molecules and Pharmaceutical Compounds  
One of the first synthetic applications of complex [PtH{((PMe2O)2H})(PMe2 OH)] (**1**) was in the preparation of atenol (**57**), a drug belonging to the group of \(\beta\)-blockers which contains a primary amide group and is commonly employed in the treatment of hypertension [63]. In particular, **1** had no difficulty in promoting the final hydration step of the nitrile intermediate **56**. Thus, as shown in Scheme 14, performing the reaction in a refluxing ethanol/water (1:1 _v/v_) mixture, and using a very low catalyst loading of 0.0001 mol%, atenol could be selectively obtained in 93% yield [64]. The steroidal compound eplerenone (**60**) is an orally-active aldosteroneene antagonist featuring a canrenone-type structure that is also used for the treatment of hypertension and heart failure [65, 66]. The synthesis of **60** has been the subject of several patents. In one of them, the Parkins catalyst was successfully employed to transform the advanced intermediate 7\(\alpha\)-cyano-9(11)\({}^{\Delta}\)-canrenone **58** into 7\(\alpha\)-carbamoyl-9(11)\({}^{\Delta}\)-canrenone **59** (Scheme 15) [67]. Conversion of the amide unit of **59** to the corresponding carboxylic acid, followed by esterification, or direct alcoholysis of the amide to the ester, completed the synthesis of **60**. Antagonists of the kappa opioid receptor have great therapeutic potential for the treatment of a range of central nervous system diseases and disorders, including, for example, schizophrenia, depression, and anxiety [68, 69, 70]. Quite recently, 8-azabicyclo[3.2.1]octan-3-yloxy-benzamides, as exemplified by **61** in Figure 5, were identified by [PERSON] and co-workers as potent and selective kappa opioid receptor antagonists [71]. In an additional SAR study, the same authors synthesized a large number of related compounds, such as **62** and **63**, in which the benzamide unit was generated by hydration of the corresponding nitrile with the Parkins catalyst [72].