Chemistry Of Tetrathiomolybdate : Application In Organic Synthesis

Abstract

The thesis entitled “Chemistry of Tetrathiomolybdate: Applications in Organic Synthesis” is divided in to six chapters Chapter 1: Synthesis of -amino disulfides, cystines and their direct incorporation into peptides mediated by tetrathiomolybdate In this chapter, we report a simple method for direct access to β-amino disulfides by regioselective ring opening of sulfamidates with benzyltriethylammonium tetrathiomolybdate [BnEt3N]2MoS4. The versatility of this reaction has been shown by preparing a number of β-amino disulfides having different N-protecting groups and the stability of these protecting groups under the reaction conditions has been evaluated. This methodology is also extended to the synthesis and direct incorporation cystine and 3, 3′-dimethyl cystine derivatives into peptides. Chapter 2: Unusual reactivity of tetrathiomolybdate: A new entry to the synthesis of b-aminothiols In this chapter, we disclose a simple and highly efficient method for the synthesis of β and γ-amino thiols via regioselective ring opening of sulfamidates with tetrathiomolybdate 1. The scope and generality of this methodology has been exemplified by synthesizing a carbohydrate derived β-aminothiol. This methodology has also been extended to the synthesis of isocysteine derivatives in optically pure form. Chapter 3: Part 1: Synthesis of β-aminodiselenides via sequential one-pot, multistep reactions mediated by tetrathiomolybdate In this chapter, we have demonstrated that a variety of N-alkyl-β-aminodiselenides can be synthesized in high yield from appropriate sulfamidates under mild reaction conditions using potassium selenocyanate and tetrathiomolybdate [BnEt3N]2MoS4 via a sequential one-pot multistep process. The compatibility of different protecting groups under the reaction conditions has been discussed. Chapter: 3 Part 2: Synthesis of unnatural seleno amino acids and their direct incorporation into peptides In this chapter, we have demonstrated the first and general method for the synthesis of selenocystine, 3, 3'-dialkylselenocystine, isoselenocystine and their direct incorporation into peptides using a one-pot multistep reaction strategy mediated by tetrathiomolybdate. Chapter 4: Synthesis and functionalization of cysteine, selenocysteine and their derivatives via the formation of unsymmetrical disulfide and sulfur-selenium bond. In this chapter, we present a novel one-pot multi component strategy for the synthesis and functionalization of cysteine, selenocysteine and their derivatives via unsymmetrical disulfides and sulfur-selenium bond formation. Chapter 5: Part 1: A novel method for the synthesis of thioacetates employing benzyltriethylammonium tetrathiomolybdate and acetic anhydride In this chapter, we report a simple and efficient methodology for the synthesis of thioacetates using benzyltriethylammonium tetrathiomolybdate [BnEt3N]2MoS4 and acetic anhydride as the key reagents, starting from alkyl halides in a multi step, tandem reaction process. The application of this methodology for the synthesis of orthogonally protected cysteine derivatives and anomeric β-thioglycosides has also been demonstrated. Chapter 5: Part 2: One-pot synthesis of β-aminothioacetates using benzyltriethyl-ammonium tetrathiomolybdate and acetic anhydride. In this chapter, we have demonstrated a simple and efficient method for the synthesis of β-amino thioacetates and pseudo thioinositol derivatives, via ring opening of aziridines and aziridino epoxides using tetrathiomolybdate 1 and acetic anhydride as key reagents. Chapter 6: Simple and efficient synthesis of allo and threo-3, 3'-dimethylcystine derivatives in optically pure form In this chapter, we have presented a simple and efficient methodology for the synthesis of allo-3,3'-dimethylcystine and threo-3,3'-dimethylcystine derivatives in optically pure form using L-threonine as the chiral pool and benzyltriethylammonium tetrathiomolybdate 1 as the key reagent. (For structural formula pl see the pdf file)