Phosphoric acids and their derivatives

Steroids possessing one or two isolated or conjugated double bonds are converted into their dihydrogen phosphates when brought into contact with (l-phenyl-l,2-dibromoethyl)phosphonic acid in the presence of ethyldiisopropyl-amine. The reactions presumably involve monomeric metaphosphate ion as the effective phosphorylating agent.  

Reagents i, (MeO)2POSiMe3 ii, MegSiBr iii, MegN N iv, Br v, NaOEt ir, EtOH-EtoO  

A series of about 35 bicyclic phosphates (20) has been prepared conventionally for spectroscopic examination and biological assessment.  

The 2-oxoazetidine-l-phosphonic acids (22) have been prepared by monodealkylation of the corresponding dialkyl esters with thiourea. The acid (22 R = R = H) was obtained, as its monoanilinium salt, by reaction of its bis-(trimethylsilyl) ester with aniline in ether.  

Cyclization of the anions from the /ra j-2-amino-5-chloromethyl-2-oxo-1,3,2-dioxaphosphorinans (23) in boiling xylene, yields the 7-aza-2,6-dioxa-l-phosphabicyclo[2.2.2]octanes (24 R = Bu , Ph, or PhCHa).  

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Synthesis of Phosphoric Acids and Their Derivatives. - The individual Rp-and Sp- isomers of the organophosphate triesters (1-6) were synthesized and isolated on a preparative scale through the kinetic resolution of racemic mixtures via the hydrolysis of a single enantiomer by the bacterial phosphotriesteraze (PTE).i... 

Synthesis of Phosphoric Acids and Their Derivatives. A selective and mild synthetic route to long or functionalized chained dialkyl phosphates (l)-(5) has been reported (Figure 1). ... 

Reactions of Phosphoric Acids and Their Derivatives. - Numerous investigations of phosphate ester hydrolysis continue to be reported. The hydrolysis between 1.5 < pH < 4 of five- and six-membered cyclic phosphoramides (71) has been followed by UV and NMR spectroscopy. Small differences in hydrolysis reactivity for n = 5 and n = 6 constitutes evidence for syn lone pair catalysis. The product ratios from the hydrolysis shows that in the five-membered rings the main product is the one produced by endocyclic cleavage meanwhile, in the six- membered cyclic phosphoramide the kinetic product is the one produced by exocyclic cleavage. The syn orientation of two electron pairs on nitrogen stabilizes the transition state of water approach to the phosphoramides by ca. 3 kcal/moN when compared to the orthogonal attack. (Scheme 12). ... 

Reactions of Phosphoric Acids and their Derivatives.- Addition of alcohols (ROH) to diethyl [2,2-difluoro-l-(trifluoromethyl)vinyl] phosphate yields the ether esters (64). Other fluorovinyl phosphates (65 R = F or CF, R = hexyl, cyclohexyl, or Ph) are cleaved by LiAlH /CuBr or by LiAlH /Br2 in THF at -78° to give the ketones (66) the same esters are also cleaved by... 

Synthesis of Phosphoric Acids and their Derivatives. - Among various approaches to phosphate esters the phosphorylation of phenols with dialkyl cyanophosphonate and the synthesis of triaryl phosphates under phase-transfer conditions are worthy of mention. Mixed trialkyl phosphates are also reported to be formed by brief cathodic electrolysis of the reaction of dialkyl phosphonates with aromatic aldehydes and ketones, presumably by rearrangement of the initial a-hydroxy compounds. Further reports have appeared of the generation of metaphosphates by various methods. The synthesis of analogues 1 of famesyl pyrophosphate which incorporate photoactive esters has been reported both compounds are competitive inhibitors of farnesyl transferase. 

Synthesis of Phosphoric Acids and Their Derivatives. - A series of monoalkyl and dialkyl phosphorus acid chiral esters have been synthesised for use as carriers for the transport of aromatic amino acids through supported liquid membranes. The compounds acted as effective carriers but enantio-separation was at best moderate. A range of phosphono- and phosphoro-fluoridates have been prepared by treatment of the corresponding thio- or seleno- phosphorus acids with aqueous silver fluoride at room temperature (Scheme 1). In some cases oxidation rather than fluorination occurred. Stereospecifically deuterium-labelled allylic isoprenoid diphosphates, e.g. (1), have been synthesised from the corresponding deuterium-labelled aldehyde by asymmetric reduction, phosphorylation and Sn2 displacement with pyrophosphate (Scheme 2). ... 

Synthesis of Phosphoric Acids and their Derivatives.-New approaches to the preparation of dialkyl phosphorofluoridates include the treatment of a vinyl phosphate, e.g.,(l), or an irninophosphace, e.g.,(2), with triethylamine tris(hydrogen fluoride) when the alkyl group consists of a suitably protected nucleoside, the reaction between mono(crimethylsilyl) phosphite in pyridine and sulphuryl chloride fluoride at -30° has been successfully explored. Dibenzyl phosphorofluorldate, hitherto unreported, has been obtained from tecrabenzyl diphosphate and caesium fluoride, and also from the reaction between dibenzyl hydrogen phosphate and 2-fluoro-N-methylpyridinlum tosylate. ... 

Reactions of Phosphoric Acids and their Derivatives. - The rearrangement of [(trimethylsilyl)methyl] phosphates to their ethyldimethylsilyl isomers is already known the mechanism of the process has now been examined in more detail and is thought to involve attack by phosphoryl oxygen at the silicon atom with migration of an alkyl group as indicated in Scheme 2. Diphenyl... 

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