Phenylsulfanyl moiety

A less common approach to the synthesis of phosphinates is the reaction of electrophilic phosphonates with carbon nucleophiles such as Grignard reagents or lithium enolates. For example, the phosphinic acid analogue 71 of the amino acid statine was synthesized by displacement of tert-butyl lithioacetate on a 5-phenyl phosphonothioate 70 (Scheme 23)d104l The racemic diastereomers of the 5-phenyl phosphonothioate were obtained in pure form, and the displacement of the phenylsulfanyl moiety was found to be stereospecific, although the stereocenter at phosphorus would later be lost on hydrolysis of the ester. A similar displacement reaction has been described using the p h osp h on och I ori d ate.1711... 

The effect of several electron-withdrawing substituents has been utilized to synthesize cyclopropylsilanes. The best results have been achieved with the arylcarboxylate, triphenylphos-phonium, and phenylsulfanyl moieties other groups utilized include the alkoxycarbon-... 

The (l5)-phenyl-2-(phenylsulfanyl) moiety could be installed easily by the treatment of a sugar alcohol with l-phenyl-2-pheny Ithioethyl acetate 1 in the presence of BF3 -OEt2 with overall retention of configuration (eq 2). 

Treatment of an epimeric mixture of 4-substituted 2-(trimethylsilyloxy)-5-phenyl-3-phenylthio-l,4-oxazine 363 with ZnBr2 led to the stereoselective formation of perhydropyrido[2,l-c][l,4]oxazine 365 via the iminium ion 364 the phenyl-bearing stereocenter-directed addition of the olefinic double bond from the P-face of the cyclic moiety <1997SL799, 1998T10309>. Similarly, an epimeric mixture of (4A, 9a.S )-l -tnmcthylsilyloxyM-phcnyl-3,4,6,7-tetra-hydropyrido[2,1 / 1,4]oxazinc was prepared by cyclization of (Z)-5(A)-phenyl-3-phenylsulfanyl-2-trimethylsilyloxy-... 

Alternatively, the use of an auxiliary with an (f )-stereochemistry at the phenyl-2-(phenylsulfanyl)ethyl moiety will lead to the formation of a 1,2-traro-glycoside because in this case the trans-decalin system will exert unfavourable steric interactions. The proposed mechanism has been supported by computational studies.39... 

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