4-Methoxy-5,6-dihydro-2H-pyrane

Hydroxyl protection /io-Butyl chloroformate. 4-Methoxy-5-6-dihydro-2H-pyrane. 

Hydroxyl group Adamantane-l-carboxylic acid chloride. 0-Benzoylpropionic acid. Ethyl vinyl ether. 4-Methoxy-5,6-dihydro-2H-pyrane. p-Nitrophenyl chloroformate. 

O-Deacetylation. 4-Methoxy-5,6-dihydro-2H-pyran added at 20 to a stirred soln. of 3, 5 -di-0-acetyluridine and p-toluenesulfonic acid in anhydrous dioxane, the... 

S,6S-6-Benzyloxymethyl-2-methoxy-5,6-dihydro-2H-pyran 4 by Asymmetric Synthesis [24,50] (Scheme 11)... 

The basic cycloadduct, butyl 2-methoxy-5,6-dihydro-2//-pyran-6-carboxylate 2a, can be reduced to 6-hydroxymethyl-2-methoxy-5,6-dihydro-2H-pyran 2b. Both 5,6-dihydro-2ff-pyrans 2a and 2b can be converted in several ways to sugars. c/s-Hydroxylation or epoxidation, followed by basic (or acidic) opening of epoxides with various nucleophilic reagents leads to various 4-deoxyhexoses 3b [18]. Dihydropyran 2b can be transformed in a... 

It was shown earlier that 2-methoxy-5,6-dihydro-2H-pyrans (279, R = Me R = H, COzBu) readily added methanol across the double bond, forming mixtures of stereoisomeric 2,4-dimethoxytetrahydropyrans. This addition reaction was extended to acetic acid, which was added in the presence of sulfuric acid to 6-acetoxy-methyl-2-methoxy-5,6-dihydro-2H-pyran (326,R-... 

A variety of racemic aminodideoxypentopyranoses have been synthesised from 2-methoxy-5,6-dihydro-2H-pyran (85), primarily by manipulating the known products of epoxidation - azide ring opening as exemplified in Scheme 24 for the synthesis of the 2-amino-2.4-dideoxv-DL-threo-Dentoside (86). These amino-sugars... 

The racemic 4-deoxy-pentopyranosylamines derivatives (2) and (3) have oeen synthesized from 2-methoxy-5,6-dihydro-2H-pyran (4) (Scheme 1) and converted into their ureido-derivatives by reaction... 

H-Pyran 6-(l-Ethyl-pentyliden)-4-methoxy-5,6-dihydro- VII/4. 195 Xanthen 4a-Hydroxy-dodecahydro-VI/4. 340, 368... 

The steric effects involved in the cis-hydroxylation of 5,6-dihydro-2H-pyrans substituted at positions 6 and/or 2 with aqueous potassium permanganate were studied by Mochalin and co-workers. It was found that the reaction course is dependent on the steric hindrance exerted by the bulky substituent at C-2 both OH groups enter preferentially trans with respect to that substituent. In consequence, products of (x-lyxo or -erythro configuration are obtained in the case of di- or mono-substituted substrates. However, in the case of 5,6-dihydro-2-methoxy-2H-pyran, both possible stereoisomeric products, methyl 4-deoxy-a-and p-DL-eo t o-pentopyranosides, were formed in approximately equal amounts. 

Crude methyl 6-benzyloxy-5-hydroxy-2-decynoate added to a soln. of Na in methanol and stirred 22 hrs. at 25° -> 4-methoxy-5,6-dihydro-6-(l-benzyloxy-pent-l-yl)-2H-pyran-2-one. Y 82%. F. e., also from the acids, s. R. M. Carlson and A. R. Oyler, Tetrah. Let. 1974, 2615 5,6-dihydro-2-pyrones s. a. J. Org. Chem. 40,1610 (1975). 

H- Pyran, rrans-2-methoxy-4-methyl-3,4-dihydro-conformation, 3, 630 2H-Pyran, 4-methyl-5,6-dihydro-photolysis, 3, 719 2H-Pyran, 6-methyl-3,4-dihydro- C NMR, 3, 586... 

H-Pyran 6-(1-tert.-Butyloxycarbo-nylamino-ethyl)-2-methoxy-5,6-dihydro- E21c, 2932 (l-OR-1,3-dien 4 RHN-CCHR-CHO)... 

Arentzen, R., YanKui,Y.T. and Reese, C.B. (1975) Improved procedures for the preparation of tetrahydro-4H-pyran-4-oneand 5,6-dihydro-4-methoxy-2H-pyran. Synthesis, 509-510. 

The reactions of 5,6-dihydro-2-methoxy-2H-pyran (101) with 1,3-dibromo-5,5-dimethylhydantoin in ether-methanol,137 and with ethanesulfenyl chloride,138 have been described by Baldwin and Brown. The former reaction gave a 2 1 mixture of the isomers 3/3-bromotetrahydro-2a ,4a-dimethoxypyran (102) and 3a-bromotetrahy-dro-2a,4/3-dimethoxypyran (103), respectively the structures and favored conformations of the isomers are shown. The reaction of ethanesulfenyl chloride with 5,6-dihydro-2-methoxy-2H-pyran (101)... 

Chemical Name (R-(E))-5,6-Dihydro-4-methoxy-6-styryl-2H-pyran-2-one Common Name Cavain Gonosan Kavain Kava pyrone Kawain Structural Formula ... 

By condensation of the mixture 1400 g ethyl ester of bromoacetoacetic acid, 700 g bromosuccineimide, 500 ml benzene and 350 mg zinc was prepared (R)-5,6-dihydro-4-methoxy-6-styryl-2H-pyran-2-one melting point 157°C, yield 60-70%. 

Propinsaure 3-Ethoxy- -methylester E15/3, 3213 (H - Li - COOR) 2H-Pyran 4-Methoxy-2-oxo-5,6-dihydro- VI/2, 671 4H-Pyran 2-Carboxy-5,6-dihydro-VI/4, 87... 

H-Pyran 6-(l-tert.-Butyloxycarbo-nyl-amino-ethyl)-4-methoxy-2-oxo-5,6-dihydro- E21c, 2933 [RHN-CHR-CHO + 1,3-(OR)2 — 1 -OSiR3 — 1,3-dien]... 

The structure of pironetin was determined to be (5/ ,6/ )-5-ethyl-5,6-dihydro-6[(jE )-(2/ ,35,4/ ,55)-2-hydroxy-4-methoxy-3,5-dimethyl-7-nonenyl]-2H-pyran-2-one by FAB-MS, H and 13C NMR, COSY, COLOC, DEPT, IR, X-ray crystallographic analyses and adapted Mosher s method to determined the absolute configuration [74]. The biosynthesis of pironetin appeared to involve assembly of acetate, propionate and butyrate precursors. Four fermentation experiments were carried out in order to determine the biosynthetic origin of the carbon skeleton and oxygen atoms of pironetin. [1-13C] Acetate, [2-13C]acetate, [1,2-13C] acetate, [l-13C]propionate, [l-1 C]butyrate and L-[methyl-I3C]methionine were led separately to Streptomyces sp. culture and pironetin was isolated and purified. Analysis of pironetin by 13C NMR showed that pironetin was derived from four acetate units, two propionate units, one butyrate unit and one methyl unit of methionine [78] (Fig. 4). 

Sharpless oxyamination reagent, composed of chloramine-T and a catalytic quantity of osmium tetraoxide, was reacted with a series of 6-substituted 5,6-dihydro-2-methoxy-2H-pyrans. Both regioisomeric methyl 2,4-dideoxy-2-p-to-luenesulfonylamido- and 3,4-dideoxy-3-p-toluenesulfonylamido DL-/yjro-hexo-pyranosides (346 and 347) were obtained in yields of 40-60%, with the latter distinctly prevailing in mixtures. 

Ethyl-5,6-dihydro-6- 2-hydroxy-4-methoxy-3,5-dimethyl-7-nonenyl)-2H-pyran-2-one, 9CI. NK 10958. PA 48153C [151519-02-7]... 

For the purposes of workup, it will appear as if two compounds are present with different Rf values, melting points, etc. This has been overcome by replacing 2,3-dihydropyran with 5,6-dihydro-4-methoxy-2H-pyran. The THP ether product is symmetrical. 

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