Spiro-oxirane

Although steroidal spiro oxiranes are difficult to obtain stereochemically pure by peracid epoxidations of exocyclic methylenes,the recently developed methylene transfer reagents, dimethylsulfonium methylide and di-methylsulfoxonium methylide in tetrahydrofuran, proved useful in the stereoselective transformation of steroid ketones to a- and -oxiranes, (87) and (88), respectively. ... 

Methylbutanoyl)spiro[oxiran-2,3,(2,//)-pyridine]-2, 4 ( 1 //)-dione (flavipucine)... 

This again illustrates the problem of correct citation of hydrogenation. The unsubstituted spiro skeleton is structure a, named as spiro[oxiran-2,3 (2 //)-pyridine], it being necessary to introduce an indicated hydrogen (2 H) to allow for the spiro linkage. The ketone groups are... 

The bromide ion catalysed rearrangement of benzofuran dioxetane (44) yields the spiro oxirane (45) by attack of bromide ion at the 3-position of the dioxetane (94JA6713). 

Jacobson and others(390) analyzed the H-nmr spectra at 100 MHz of codeine and isocodeine derivatives, previously reported at 60 MHz,(391) in order to establish the conformation of the spiro-oxirane derived from codeinone.<200) Double irradiation and NOE experiments confirmed the structure illustrated (91). 

Diazocyclopropane converts the 16-bromo-17-oxo-compounds (174) into isomeric spiro-oxirans (175) rearrangement with boron trifluoride gave the corresponding spirocyclobutanones (176), which could be debrominated with Raney nickel."°°... 

Spiro-oxirans e.g. 78) are readily opened by 2-lithio-l,3-dithians to give derivatives (79b) which offer synthetic possibilities. ... 

The 12-membered ring macrolides are not represented by clinical agents in the United States. The most prominent members of the 14-unit rings are the erythromycins (EM) and oleandomycins. Oleandomycin (which forms a spiro-oxirane with the C8 of EM-A) and its triacetate, has been discontinued in the United States. 

The spiro-oxirane ring, in many cases, is replaceci by a CH2OR and an a-hydroxy group. In such cases, the C-18 protons are shifted from ca 2.7 and 3.10 to ca 8 4.00 and 4.50 as observed in 62-65 [35-37 while the C-3 proton, geminal to an acetyl group, appears around 6 5.20-5.4C. Table 6 gives the H and NMR data of 62-65. 

A new synthesis of the hydroazulenone (119) has been reported, from the bicyclic dione (116) (Scheme 6)." Initial conversion of (116) into the spiro-oxiran (117) by Corey s reagent (Mc2S—CH2) is followed by BF3-Et20-catalysed rearrangement via the carbo-cation (118) to the azulene derivative (119). 

Cyclodihydrocodeinone, on catalytic reduction, yields 14-methyl-C-nordihydrocodeinone (144), which, on ring expansion with diazomethane, yields 14-methyldihydrocodeinone and the related 6-spiro-oxiran, together with the corresponding seven-membered ring products of further expansion. ... 

A series of reactions of the deoxy-inosose (54) have been described standard reactions at the free hydroxy group and ketone carbonyl occur. Rjeaction with diazomethane gave a spiro-oxiran intermediate as well as the 6-oxa-bicyclo [3,2,l]-octane (55). ... 

The 2-deoxy-2-fluoro-2-hydroxymethyl-myo-inositol (58) has been synthesized via the corresponding 2-spiro-oxiran analogue. 

The proposed mechanism (Scheme 11) of the asymmetric epoxidation of a-ylideneoxindoles (97) by TBHP to cis- and frani-spiro[oxirane-oxindole] derivatives (101 and 102) had TBHP react with the catalyst (5)-a,a-diphenylprolinol (95) in the initial step forming a tight ion pair (96), which attacks the Cp carbon of the substfate (97) to give a transitory intermediary complex (98) as precursor of a long-living intermediate (99) from which (101) and (102) are derived. " 0... 

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