## 3 Application of Complex [PtH{(PMe2O)2H}(PMe2 OH)] in the Total Synthesis of Natural Products
During this synthesis the conversion of nitrile intermediate **19** into amide **20** was successfully accomplished in 87% yield using 20 mol% of the platinum complex [PtH{((PMe\({}_{2}\)O)\({}_{2}\)H)(PMe\({}_{2}\)OH)] (**1**). **Scheme 7. ** The hydration step in total synthesis of (\({}^{+}\))-geniposide. SB-203207 (**25**), an alkaloid isolated from a _Streptomices_ species by researchers in the SmithKline Beecham group, was found to show marked isoleucyl tRNA synthetase inhibition activity [39,40]. Very recently, [PERSON] and co-workers described a total synthesis of this compound starting from lactam **22**, in which the primary amide unit was generated by catalytic hydration of nitrile intermediate **23** with complex **1** (Scheme 8) [41]. As in the two previous cases, a high loading of **1** was needed to obtain the corresponding amide product **24** in high yield. SB-203207 can also be accessed by acylation of the sulfonamide unit of naturally occurring altemicidin (**26** in Scheme 8) [42]. In this context, the stereoselective synthesis of a key intermediate for altemicidin, _i.e._ amide **27** (see Scheme 8), was accomplished by [PERSON] and [PERSON] employing [PtH{((PMe2O)2H}(PMe2 OH)] (**1**) [43]. Compound **27** was obtained in quantitative yield by the hydration of the corresponding nitrile in aqueous ethanol at 75 \({}^{\circ}\)C for 12 h with 28 mol% of **1**. **Scheme 8. The Parkins catalyst in the synthesis of alkaloid SB-203207. **  
**In a synthetic approach toward the cytotoxic indole alkaloid avrainvillamide (**30**) and its dimeric form stephacidin B (**31**) [44], [PERSON] and co-workers used [PtH{((PMe2O)2H}(PMe2 OH)] (**1**) to synthesize primary amide intermediate **29** by the hydration of nitrile **28** (Scheme 9) [45,46]. The reaction proceeded cleanly in aqueous ethanol at 70 \({}^{\circ}\)C and with 20 mol% of **1**, affording **29** in 85% isolated yield. **Scheme 9. ** The Parkins catalyst in the synthesis of avrainvillamide and stephacidin B. The manzacidins are a family of marine natural products featuring a tetrahydropyrimidine carboxylic acid and an ester-linked bromopyrrole unit. This class of alkaloids has attracted significant attention due to their biological activities and unusual structure. Consequently, many groups have described the enantio- and diastereoselective synthesis of some of them [47]. In this context, [PERSON] and co-workers reported synthetic routes to manzacidin A (**34**) [48,49] and manzacidin C (**37**) [50] involving a nitrile hydration step promoted by complex [PtH{(PMe2O)2H}(PMe2 OH)] (**1**) (Scheme 10). In particular, **1** was used to transform the diastereomeric nitriles **32** and **35** into the corresponding primary amide intermediates **33** and **36**, respectively. As shown in the scheme, almost quantitative yields were achieved in both cases, performing the reactions at 80 \({}^{\circ}\)C with low catalyst loading (5 mol%). **Scheme 10. ** Hydration steps in the syntheses of manzacidins developed by [PERSON]. In the context of their synthetic studies on the icetaxane family of diterpenoids, the hydration of nitrile **38** by complex **1** was successfully employed by [PERSON] and co-workers to prepare primary amide **39**, from which the formal synthesis of icetexone (**40**) and _epi_-icetexone (**41**) could be completed (Scheme 11) [51,52]. The marine natural product psycherin (**42** in Figure 3) has attracted a great deal of attention since its discovery in 2004 due to its complex architecture, biological properties, and paucity in nature. This interest has resulted in a large number of synthetic investigations and the development of analogous molecules [53]. The Parkins catalyst [PtH{(PMeO)2H}(PMeOH)] **(1)** has been involved in some of these studies [54, 55, 56, 57, 58, 59]. In particular, in the first total synthesis of this compound, [PERSON] and co-workers employed **1** to synthesize advanced amide intermediate **43** from the corresponding nitrile [54, 55, 57].