Total synthesis of milbemycin .beta.3

Smith, Amos B.; Schow, Steven R.; Bloom, Jonathan D.; Thompson, Andrew S.; Winzenberg, Kevin N.

doi:10.1021/ja00378a045

Cited by 103 publications

(33 citation statements)

References 2 publications

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“…The gf values adopted are essentially identical for the two large extremely metal-poor halo field star surveys, and are those of NIST. Many of the older analyses use those from Smith & Raggett (1981), which scatter widely around the recent values. Thus, as is also the case for Mg I, ideally one must correct each star individually, checking which specific Mg I and Ca I lines were used and what gf values were adopted.…”

Section: The Trend Of [C/fe] Versus [Fe/h] Is Shown Inmentioning

confidence: 99%

The Chemical Evolution of the Draco Dwarf Spheroidal Galaxy

Cohen

Huang

2009

ApJ

189

261

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We present an abundance analysis based on high resolution spectra of 8 stars selected to span the full range in metallicity in the Draco dwarf spheroidal galaxy. We find [Fe/H] for the sample stars ranges from −1.5 to −3.0 dex. Combining our sample with previously published work for a total of 14 luminous Draco giants, we show that the abundance ratios [Na/Fe], [Mg/Fe] and [Si/Fe] for the Draco giants overlap those of Galactic halo giants at the lowest [Fe/H] probed, but are significantly lower for the higher Fe-metallicity Draco stars. For the explosive α-elements Ca and Ti, the abundance ratios for Draco giants with [Fe/H] > −2.4 dex are approximately constant and slightly sub-solar, well below values characteristic of Galactic halo stars. The sprocess contribution to the production of heavy elements begins at significantly lower Fe-metallicity than in the Galactic halo.Using a toy model we compare the behavior of the abundance ratios within the sample of Draco giants with those from the literature of Galactic globular clusters, and the Carina and Sgr dSph galaxies. The differences appear to be related to the timescale for buildup of the heavy elements, with Draco having the slowest rate.We note the presence of a Draco giant with [Fe/H] < −3.0 dex in our sample, and reaffirm that the inner Galactic halo could have been formed by early accretion of Galactic satellite galaxies and dissolution of young globular clusters, while the outer halo could have formed from those satellite galaxies accreted later. Stellar Sample and Stellar ParametersOur sample in the Draco dSph galaxy contains 8 stars; details are given in Table 1. It was selected from Table 2.9 of Winnick (2003) to include stars which are known radial velocity members of this satellite to the Galaxy at or near the RGB tip spanning the full range in color and in metallicity and not previously observed at high spectral resolution. Winnick measured the infrared Ca triplet in moderate resolution spectra of Draco stars obtained using the multi-fiber Hydra spectrograph at the WIYN telescope. Her sample was chosen from the photometric survey of Piatek et al. (2001) and previous radial velocity surveys (see, e.g. Armandroff, Olszewski & Pryor 1995). Only confirmed radial velocity members are listed in her table; carbon stars known to be members of Draco were excluded. She developed her own calibration of the relationship between Ca triplet indices and Fe or Ca metallicity based on data for Galactic globular clusters. Details of the calibration and related issues are discussed in the appendix. We adopt the procedures described in Cohen et al. (2002) and used in all subsequent work by the first author published to date to determine the stellar parameters for our sample of luminous Draco giants. Our T ef f determinations are based on the broad band colors V − J and V − K. The optical photometry (we use V only, the V − I color supports the deduced T ef f in most cases, but is not used) is from the SDSS (York et al. 2000) using the transformation equations of Smith e...

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Section: The Trend Of [C/fe] Versus [Fe/h] Is Shown Inmentioning

confidence: 99%

The Chemical Evolution of the Draco Dwarf Spheroidal Galaxy

Cohen

Huang

2009

ApJ

189

261

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“…Preparation of the oxazoline (12) (go%), followed by acylation in 90% yield, gave the ketone (13). 3 Treatment with allylmagnesium chloride and subsequent acid hydrolysis yielded the lactone (14) (70%). Ozonolysis, elimination (DBU), and methylation yielded the required aldehyde (4), Y , , , .…”

mentioning

confidence: 99%

“…-7.8 (lOH, m, Ar), in good overall yield (70-80%). The synthesis was completed using a small modification of the protocol developed by Smith et aZ 3. In our hands desilylation was best achieved with Bun4NF in refluxing THF for 10 min.…”

mentioning

confidence: 99%

The total synthesis of (+)-milbemycin β₃

Baker¹,

O'Mahony²,

Swain³

1985

J. Chem. Soc., Chem. Commun.

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We report the total synthesis of (+)-milbemycin p3 from the optically pure precursors spiroacetal (3) and vinyl iodide (Z), and the aromatic aldehyde (4).The milbemycins comprise a group of natural products isolated from cultures of Streptomyces B-41-146, of which milbemycin p3 (1) is the simplest.1 Interest in these compounds has increased since the isolation and identification of a structurally related series of macrolides, the avermectins.'

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“…94 The readily available flavor constituent cyclotene (368) (Scheme 2.28) was reduced and isomerized to 2-methyl-2-cyclopenten-1-one (369) in 64% yield. Addition of dimethyl cuprate followed by isomerization and Baeyer-Villiger oxidation gave the racemic 6-lactone 370 (86%).…”

Section: J Milbemycin P3mentioning

confidence: 99%