Oxidation stereospecific synthesis

Watanabe, A., Uchida, T., Irie, R., et al. (2004). Zr[bis(salicylidene)ethylenediaminato]-Mediated Baeyer-Villiger Oxidation stereospecific Synthesis of Abnormal and Normal Lactones, Proc. Natl. Acad. Sci. USA, 101, pp. 5737-5742 Watanabe, A., Uchida, T., Ito, K.,... 

Watanabe A, Uchida T, Irie R, Katsuki T. Zr[bis(salicylidene) ethylenediaminato]-mediated Baeyer-Villiger oxidation stereospecific synthesis of abnormal and normal lactones. Proc. Natl. Acad. Sci. USA 2004 101 5737-5742. 

Deamination, Transamination. Two kiads of deamination that have been observed are hydrolytic, eg, the conversion of L-tyrosiae to 4-hydroxyphenyUactic acid ia 90% yield (86), and oxidative (12,87,88), eg, isoguanine to xanthine and formycia A to formycia B. Transaminases have been developed as biocatalysts for the synthetic production of chiral amines and the resolution of racemic amines (89). The reaction possibiUties are illustrated for the stereospecific synthesis of (T)-a-phenylethylamine [98-84-0] (ee of 99%) (40) from (41) by an (5)-aminotransferase or by the resolution of the racemic amine (42) by an (R)-aminotransferase. 

A method for the stereospecific synthesis of thiolane oxides involves the pyrolysis of derivatives of 5-t-butylsulfinylpentene (310), and is based on the thermal decomposition of dialkyl sulfoxides to alkenes and alkanesulfenic acids299 (equation 113). This reversible reaction proceeds by a concerted syn-intramolecular mechanism246,300 and thus facilitates the desired stereospecific synthesis301. The stereoelectronic requirements preclude the formation of the other possible isomer or the six-membered ring thiane oxide (equation 114). Bicyclic thiolane oxides can be prepared similarly from a cyclic alkene301. 

A stereospecific synthesis for cw-3-hexen-l-ol starts with the ethylation of sodium acetylide to 1 -butyne, which is reacted with ethylene oxide to give 3-hexyn-l-ol. Selective hydrogenation of the triple bond in the presence of palladium catalysts yields cw-3-hexen-l-ol. Biotechnological processes have been developed for its synthesis as a natural flavor compound, e.g., [12]. 

Another stereospecific synthesis of2-deoxy-DL-en/tfiro-pentose was based10 on cis-l-(tetrahydropyran-2-yloxy)-2-penten-5-ol (156) as the substrate. cts-Hydroxylation of 156, followed by oxidation of the unprotected, primary hydroxyl group to an aldehyde group according to Barton s procedure, yielded the desired sugar 2 in low yield. 

Nitrile oxide J -I- 2 cycloaddition.1 A key step in a recent stereospecific synthesis of biotin (6) from cycloheptene (1) is an intramolecular [3 + 2]cyclo-addition of a nitrile oxide (a), obtained by dehydration of a primary nitro compound (3), preferably with phenyl isocyanate. This cycloaddilion is more efficient than the well-known olefinic nitrone cycloaddition. The carbon atoms in 6 derived from cycloheptene are marked with asterisks. 

The application of intramolecular dipolar cycloaddition reactions to the synthesis of complex natural products has recently come to be recognized as a very powerful synthetic tool, one equally akin to the intramolecular Diels-Alder reaction in its potential scope of application.69 This is particularly the case with nitrile oxides and the 1NOC reaction has been extensively utilized in total synthesis.70 The intramolecular nitrile oxide cycloaddition (INOC) generally displays exceptional regio- and stereo-chemical control which undoubtedly accounts for the popularity of this reaction. Internal cycloadditions of nitrile oxides have been found to offer a powerful solution to many problems in complex natural product synthesis.48 For example, Confalone and coworkers have utilized the INOC reaction for the stereospecific synthesis of the key amino alcohol (60), which was converted in five subsequent steps to ( )-biotin (61 Scheme 14).71... 

A stereospecific synthesis of aziridine 266 has been reported by Ittah et al. from arene oxide 1 by treatment with sodium azide, followed by tri-phenylphosphine reaction. The reaction proceeds via a phosphonium hydroxide intermediate (267).157... 

Durst and Sharma [86] have reported the stereospecific synthesis of 3-spiro-epoxyazetidin-2-ones 55 (Scheme 14). The oxidation of the diastereoisomers of compound 52 with PCC provided a single acetyl compound 3-acetyl-3-benzyloxy-azetidin-2-one 53. Nonchelation controlled L-Selectride reduction of 53 gave the isomerically pure 3-hydroxyethylazetidin-2-one as the sole reduced product, which was further converted to tosylate 54 using NaH/tosylimidazole. The debenzylation-oxirane formation sequence was conveniently performed as a single pot operation with ammonium formate, 5% Pd/C in refluxing methanol as the hydrogen transfer reagent combination. 

Testa B, Jenner P (1976) Drug metabolism chemical and biochemical aspects. Part II Biochemical aspects of drug oxidation. In Swarbrick J (ed) Drug and the pharmaceutical science. Marcel Dekker, New York, pp 271-312 Wittman MD, Kadow JK, Vyas DM (2000) Stereospecific synthesis of the major human metabolite of paclitaxel. Tetrahedron Lett 41 4729... 

A stereospecific reduction of a pseudoglycal has been used to prepare the same isomer.23 Reduction of methyl 4,6-0-benzylidene-2,3-dideoxy-/3-D-erythro-hex-2-enopyranoside (6) with lithium aluminum deuteride led to the stereospecific synthesis of 4,6-0-benzylidene-3-deoxy-D-glucal-3(S)-d (7), which, after oxidation with osmium tetra-oxide-periodate followed by debenzylidenation, gave 2-deoxy-D-erythro-Tpentose-2(S)-d (2-deoxy-2-deuterio-D-arabinose) (8). Reduc-... 

However, in recent years, it has become apparent that several photoinduced oxidation reactions do not involve singlet oxygen as the reactive intermediate, and, consequently, the reaction products cannot be accounted for the mechanisms shortly reported above. Moreover, since the first report on the photochemical stereospecific synthesis of the most fascinating peroxide derivatives, i.e., 1,2-dioxetanes [32], it clearly appeared, with a few notable exceptions [33,38], that only electron-rich olefins, such as enamines, enol ethers, and thio-substituted... 

An expeditious stereospecific synthesis of the protoilludane skeleton has been actively pursued by Matsumoto s group. In his first approach (Scheme 42),307 bicyclooctanone 274 was smoothly elaborated in classical fashion. Using a five-step sequence to effect a 1,2-carbonyl transposition with retention of a hydroxyl group at the original carbonyl site, these workers then prepared 275. Oxidation of this intermediate followed by end acetylation afforded 276. When this enone was irradiated... 

Another possible approach for stereospecific synthesis is the use of zeolites with appropriate transition metal fi amework ions to effect asymmetric chemistry. One basis of the prerequisite asymmetry may be the disruption of the local symmetry introduced by the size and the electronic structure of the chosen transition-metal ion impurity contained in the ciystal fi amework. additional chemical manipulations, such as the replacement of the oxide ligand or the addition of activating ligands, may result in desired catalytic activity and selectivity and the maintenance of uniformity among active sites. 

The early attempts to use relatively easily available diastereomerically pure nucleoside 3 -0-(2-cyanoethyl-AT,AT-diisopropylphosphoramidite) monomers for the stereospecific synthesis of PS-Oligos failed because of inevitable racemiza-tion of Pm intermediate caused by an excess of lff-tetrazole necessary for efficient elongation of oligonucleotide chain [13]. An idea to use for that purpose appropriately protected nucleosides functionalized at 3 -0 position with 2-thio-1,3,2-oxathiaphospholane moiety arose from the studies on the reactions of di-substituted phosphorothioates with oxiranes [14,15], and in particular from the observation that PS-PO exchange in 0,0-diphenyl phosphorothioate (8) upon treatment with ethylene oxide in methanol solution resulted in formation of... 

Since the discovery of the illudane-type sesquiterpenoids, a number of related compounds have been isolated, viz., illudalic acid (167), illudinine (168), and dihydroilludin S (169, R = a-OH). The absolute stereochemistry of illudin S (169, R = =0) has been determined. A sequel to the successful stereospecific synthesis of illudin M (170) has been reported by Matsumoto et in which the diacetate (171, R = Ac), which had previously been prepared in the first synthesis, was selectively hydrolysed to the monoacetate (171, R = H). This compound was converted in three steps to the diacetate (172), which, after another selective hydrolysis, Jones oxidation, and acetate hydrolysis, yielded illudin M (170). 

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