Absolute configuration synthesis

J Das, MF Haslanger, JZ Gougoutas, MF Malley. Synthesis of optically active 7-oxabicyclo[2.2.1]heptanes and assignment of absolute configuration. Synthesis 12 1100-1112, 1987. 

Bezuidenhoudt BCB, Brandt EV, Roux DG 1981 A novel a-hydroxydihydro-a-chalcone from the heartwood of Pterocarpus angolensis D.C. Absolute configuration, synthesis, photochemical transformations. J Chem Soc Perkin Trans I. 263-269... 

Synthesis. In the syntheses of T and its congeners, formation of the stericaHy hindered diaryl ether core is difficult, as is the introduction of the alanyl side chain (or the preservation of its L (3) absolute configuration) and iodination to the desired degree (T or T. ... 

Azetidine, 7V-bromo-, 7, 240 Azetidine, AT-r-butyl- N NMR, 7, 11 Azetidine, AT-t-butyl-3-chloro-transannular nucleophilic attack, 7, 25 Azetidine, 3-chloro-isomerization, 7, 42 Azetidine, AT-chloro-, 7, 240 dehydrohalogenation, 7, 275 Azetidine, 7V-chloro-2-methyl-inversion, 7, 7 Azetidine, 3-halo-synthesis, 7, 246 Azetidine, AT-halo-synthesis, 7, 246 Azetidine, AT-hydroxy-synthesis, 7, 271 Azetidine, 2-imino-stability, 7, 256 Azetidine, 2-methoxy-synthesis, 7, 246 Azetidine, 2-methyl-circular dichroism, 7, 239 optical rotatory dispersion, 7, 239 Azetidine, AT-nitroso-deoxygenation, 7, 241 oxidation, 7, 240 synthesis, 7, 246 Azetidine, thioacyl-ring expansion, 7, 241 Azetidine-4-carboxylic acid, 2-oxo-oxidative decarboxylation, 7, 251 Azetidine-2-carboxylic acids absolute configuration, 7, 239 azetidin-2-ones from, 7, 263 synthesis, 7, 246... 

Diisocyanoadociane, a novel marine-derived diterpenoid, was analyzed retrosynthetically using the intramolecular Diels-Alder transform as T-goal concurrently with topological and stereochemical guidance. The enantioselective synthesis outlined below allowed assignment of absolute configuration. 

The synthesis of key intermediate 12, in optically active form, commences with the resolution of racemic trans-2,3-epoxybutyric acid (27), a substance readily obtained by epoxidation of crotonic acid (26) (see Scheme 5). Treatment of racemic 27 with enantio-merically pure (S)-(-)-1 -a-napthylethylamine affords a 1 1 mixture of diastereomeric ammonium salts which can be resolved by recrystallization from absolute ethanol. Acidification of the resolved diastereomeric ammonium salts with methanesulfonic acid and extraction furnishes both epoxy acid enantiomers in eantiomerically pure form. Because the optical rotation and absolute configuration of one of the antipodes was known, the identity of enantiomerically pure epoxy acid, (+)-27, with the absolute configuration required for a synthesis of erythronolide B, could be confirmed. Sequential treatment of (+)-27 with ethyl chloroformate, excess sodium boro-hydride, and 2-methoxypropene with a trace of phosphorous oxychloride affords protected intermediate 28 in an overall yield of 76%. The action of ethyl chloroformate on carboxylic acid (+)-27 affords a mixed carbonic anhydride which is subsequently reduced by sodium borohydride to a primary alcohol. Protection of the primary hydroxyl group in the form of a mixed ketal is achieved easily with 2-methoxypropene and a catalytic amount of phosphorous oxychloride. 

Having retraced the efficient and elegant sequences of reactions that have led to the synthesi of key intermediates 11 and 12, we are now in a position to address their union and the completion of the total synthesis of erythronolide B. Taken together, intermediates 11 and 12 contain all of the carbon atoms of erythronolide B, and although both are available in optically active form of the required absolute configuration, racemic 11 and enantiomerically pure 12... 

An important stereochemical issue presents itself here. A priori, an aldol condensation between intermediates 2 and 3 could result in the formation of a mixture of diastereomeric aldol adducts, epi-meric at C-7, with little or no preference for a particular stereoisomer. Cram s rule2,4 predicts the formation of aldol adduct 43. This intermediate possesses the correct absolute configuration at C-7, and it should be noted that Kishi et al. had demonstrated during the course of their monensin synthesis that a similar aldol condensation produced the desired C-7 epimer as the major product.12... 

The identity in sign and similarity in optical rotations of sultones (+)-52A,B, obtained from (—)-49A and (+)-49B, indicate that the absolute configuration of the y-carbon in both sultones as well as in both sultines is the same. In conclusion, the authors suggested113,114 that of the four possibilities shown below, y-sultines 48A-51A and 48B-51B may be assigned the (R)c-(Sf and (R)c-(Rf absolute configurations, respectively. Although initiated by mechanistic interest, this study has also resulted in a new method for selective synthesis of... 

Madindoline A (7) and B (ent-8) are potent inhibitors of interleukin 6. In a total synthesis [21] that also intended to determine the relative and absolute configurations of these novel antibiotics, the densely functionalized cyclopen-tene-l,3-dione ring of 7 and 8 was elaborated via RCM of diene-diol 2 (Scheme 1). 

Carbohydrate Components of Antibiotics. Part III. Synthesis of 3.6-Dideoxy-3-dimethylamino- 3-D-glucose Hydrochloride Monohydrate the Absolute Configuration of Mycaminose, A. B. Foster, T. D. Inch, J. Lehmann, M. Stacey, and J. M. Webber, /. Chem. Soc., (1962) 2116-2118. 

Jerina DM, PJ van Bladeren, H Yagi, DT Gibson, V Mahadevan, AS Neese, M Koreeda, ND Sharma, DR Boyd (1984) Synthesis and absolute configuration of the bacterial cis-1,2-, cis-8,9-, and cis-10, 11-dihydrodiol metabolites of benz[a]anthacene by a strain of Beijerinckia. J Org Chem 49 3621-3628. 

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