苯并[G]屈 | 196-78-1

• 分子结构分类: 有机化合物 - 苯类化合物 - 菲及其衍生物
• 中文名称: 苯并[G]屈
• 中文别名: 苯并屈；苯[G]并屈
• 英文名称: benzo[g]chrycene
• 英文别名: benzo[g]chrysene；Benzochrysen；benzochrysene；1,2:3,4-Dibenzphenanthren；pentacyclo[12.8.0.02,7.08,13.015,20]docosa-1(14),2,4,6,8,10,12,15,17,19,21-undecaene
• CAS: 196-78-1
• 化学式: C₂₂H₁₄
• 分子量: 278.353
• InChiKey: JZOIZKBKSZMVRV-UHFFFAOYSA-N

物化性质

• 熔点：
  126-127℃
• 沸点：
  525℃
• 密度：
  1.232
• 闪点：
  265℃
• 颜色/状态：
  Needles from acetic acid
• 溶解度：
  In water, 1.03X10-2 mg/L at 25 °C (est)
• 蒸汽压力：
  2.03X10-8 mm Hg at 25 °C (est)
• 分解：
  When heated to decomposition it emits acrid smoke and irritating fumes.
• 保留指数：
  483.61;483.57

计算性质

• 辛醇/水分配系数(LogP)：
  7
• 重原子数：
  22
• 可旋转键数：
  0
• 环数：
  5.0
• sp3杂化的碳原子比例：
  0.0
• 拓扑面积：
  0
• 氢给体数：
  0
• 氢受体数：
  0

ADMET

代谢

多环芳烃在哺乳动物细胞中的代谢会导致生成被认为是终极致癌物的邻二醇环氧物，如果环氧环位于母体化合物的湾区或峡区。在当前研究中，chrysene、dibenz[a,h]anthracene和benzo[a]pyrene的湾区二醇环氧物的个体对映异构体以及benzo[c]phenanthrene、benzo[c]chrysene和benzo[g]-chrysene的峡区二醇环氧物已经与GSH一起在人类谷胱甘肽转移酶GSTM1-1（一个mu类酶）和GSTP1-1（一个pi类酶）的存在下进行了孵化。正如之前用GSTA1-1（一个alpha类酶）所展示的，M1-1和P1-1对本研究中的许多二醇环氧物表现出相当大的活性，尽管在催化效率和立体选择性方面观察到很大的变化。对于GSTM1-1，特别是湾区二醇环氧物的syn-对映异构体通常比峡区类似物更有效地与GSH结合。GSTM1-1对于在环氧环的苄基位置具有R-构型的对映异构体的结合显示出从无偏好（50%）到高度偏好（大于或等于90%）的立体选择性。对于GSTP1-1，该酶对湾区和峡区二醇环氧物都表现出了相当大的活性，并且在大多数情况下对anti-对映异构体有偏好。与GSTM1-1和之前对GSTA1-1的展示相反，GSTP1-1对于在苄基环氧碳上具有R-构型的对映异构体的结合显示出独有的偏好。对于GSTM1-1和GSTP1-1，化学上最活性的二醇环氧物，即反式-7,8-二羟基-9,10-环氧-7,8,9,-10-四氢苯并[a]芘的(+)-syn-对映异构体（BPDE），是最好的底物。与GSTA1-1一样，化合物的化学活性和亲脂性与其催化效率之间没有明显的相关性。二醇环氧物在GSTP1-1和-A1-1活性位点的分子建模与基于功能研究的假设相一致，即GSTA1-1的H位点可以容纳不同大小的立体异构体。此外，将anti-和syn-BPDE的对映异构体在GSTP1-1的活性位点进行建模，为对在苄基环氧碳上具有R-构型的对映异构体的独有偏好提供了解释。这些异构体可以被紧密地适配在H位点，靠近GSH硫，而具有相反立体化学的异构体则不能。

Metabolism of polycyclic aromatic hydrocarbons in mammalian cells results in the formation of vicinal diol epoxides considered as ultimate carcinogens if the oxirane ring is located in a bay- or fjord-region of the parent compound. In the present study, individual stereoisomers of the bay-region diol epoxides of chrysene, dibenz[a,h]anthracene, and benzo[a]pyrene as well as of the fjord-region diol epoxides of benzo[c]phenanthrene, benzo[c]chrysene, and benzo[g]-chrysene have been incubated with GSH in the presence of human glutathione transferases GSTM1-1 (a mu-class enzyme) and GSTP1-1 (a pi-class enzyme). As previously shown with GSTA1-1 (an alpha-class enzyme) both M1-1 and P1-1 demonstrate considerable activity toward a number of the diol epoxides studied, although a great variation in catalytic efficiency and enantioselectivity was observed. With GSTM1-1, the bay-region diol epoxides, in particular the syn-diastereomers were in most cases more efficiently conjugated with GSH than the fjord-region analogues. GSTM1-1 demonstrated an enantioselectivity ranging from no preference (50%) to high preference (> or = 90%) for conjugation of the enantiomers with R-configuration at the benzylic position of the oxirane ring. With GSTP1-1, the enzyme demonstrated appreciable activity toward both bay- and fjord-region diol epoxides and, in most cases, a preference for the anti-diastereomers. In contrast to GSTM1-1 and as previously shown for GSTA1-1, GSTP1-1 showed an exclusive preference for conjugation of the enantiomers with R-configuration at the benzylic oxirane carbon. With both GSTM1-1 and GSTP1-1, the chemically most reactive diol epoxide, the (+)-syn-enantiomer of trans-7,8-dihydroxy-9,10-epoxy-7,8,9,-10-tetrahydrobenzo[a]pyrene (BPDE), was the best substrate. As for GSTA1-1, no obvious correlation between chemical reactivity or lipophilicity of the compounds and catalytic efficiencies was observed. Molecular modeling of diol epoxides in the active sites of GSTP1-1 and -A1-1 is in agreement with the assumption, based on functional studies, that the H-site of GSTA1-1 can accommodate stereoisomers of different sizes. Further, modeling of the enantiomers of anti- and syn-BPDE in the active site of GSTP1-1 provides an explanation for the exclusive preference for the enantiomers with R-configuration at the benzylic oxirane carbon. These isomers could be snuggly fitted in the H-site close to the GSH sulfur, whereas those with opposite stereochemistry could not.

来源:Hazardous Substances Data Bank (HSDB)

代谢

研究了由Aroclor 1254处理的Sprague-Dawley大鼠微粒体将外消旋的苯并[c]芘-反-9,10-、苯并[g]芘-反-11,12-和二苯并[a,l]芘-反-11,12-二氢二醇代谢激活成峡湾区顺-和反-二氢二醇环氧物。由于在实验条件下峡湾区二氢二醇环氧物在酸作用下不稳定，因此通过加入过氯酸后酸水解产物的分析来确定它们的酶促形成。形成的各种立体异构四醇通过高效液相色谱（HPLC）分离，并通过与酸水解合成的顺-和反-二氢二醇环氧物得到的真实四醇的共色谱法进行鉴定，这些四醇通过核磁共振（NMR）和紫外光谱进行了表征。在标准化的条件下，苯并[c]芘、苯并[g]芘和二苯并[a,l]芘的顺-二氢二醇环氧物的酸水解形成两个四醇，其顺/反比分别为81:19、77:23和80:20，而反-二氢二醇环氧物几乎完全发生反式水解。微粒体培养中得到的立体异构四醇的比例表明，所有三种二氢二醇主要在相邻的烯丙基双键处被氧化成相应峡湾区二氢二醇环氧物的反立体异构体，占可由乙酸乙酯提取的代谢物的4-35%。为了对代谢物进行定量评估，通过用硼三钠还原相应的邻醌合成了（3）H标记的反式二氢二醇。在大鼠肝微粒体中，苯并[c]芘-反-9,10-和二苯并[a,l]芘-反-11,12-二氢二醇的代谢转化在前10分钟的培养中处于相似的低范围内（分别为6.2 +/- 1.2和3.4 +/- 1.0 nmol底物/nmol细胞色素P450/10分钟），而苯并[g]芘-反-11,12-二氢二醇的转化要高得多（20.6 +/- 2.2 nmol底物/nmol细胞色素P450/10分钟）。鉴于峡湾区二氢二醇环氧物具有强烈的内在诱变和致癌活性，我们的数据表明，即使它们形成的水平相对较低，也可能显著地贡献于母体烃的生物学活性。

Metabolic activation of the racemic benzo[c]chrysene-trans-9,10-, benzo[g]chrysene-trans-11,12- and dibenzo[a,l]pyrene-trans-11,12-dihydrodiols to fjord region syn- and anti-dihydrodiol epoxides by microsomes of Aroclor 1254-treated Sprague-Dawley rats has been examined. Since the fjord region dihydrodiol epoxides were hydrolytically unstable under the experimental conditions, their enzymatic formation was determined by analyzing the tetraols as their products of acidic hydrolysis upon addition of perchloric acid. The various stereoisomeric tetraols formed were separated by HPLC and identified by co-chromatography with authentic tetraols, which had been prepared by acidic hydrolysis of synthetically available syn- and anti-dihydrodiol epoxides and characterized by NMR and UV spectroscopy. Under standardized conditions the acidic hydrolysis of syn-dihydrodiol epoxides of benzo[c]chrysene, benzo[g]chrysene and dibenzo[a,l]pyrene resulted in the formation of two tetraols with cis/trans ratios of 81:19, 77:23 and 80:20, respectively, whereas the anti-dihydrodiol epoxides underwent almost exclusively trans hydrolysis. The proportion of the stereoisomeric tetraols obtained from microsomal incubations indicates that all three dihydrodiols are predominantly oxidized at the adjacent olefinic double bond to the anti-diastereomers of the corresponding fjord region dihydrodiol epoxides accounting for 4-35% of the ethyl acetate-extractable metabolites. To allow quantitative assessment of the metabolites (3)H-labeled trans-dihydrodiols were synthesized by reduction of the corresponding o-quinones with sodium borotritide. Metabolic conversion of benzo[c]chrysene-trans-9,10- and dibenzo[a,l]pyrene-trans-11,12-dihydrodiol by rat liver microsomes were in a similar low range during the first 10 min of incubation (6.2 +/- 1.2 and 3.4 +/- 1.0 nmol substrate/nmol cytochrome P450/10 min, respectively), whereas the conversion of benzo[g]chrysene-trans-11,12-dihydrodiol was much higher (20.6 +/- 2.2 nmol substrate/nmol cytochrome P450/10 min). Given the strong intrinsic mutagenic and carcinogenic activity of the fjord region dihydrodiol epoxides, our data indicate that their formation, even at a relatively low level, may contribute significantly to the biological activity of the parent hydrocarbons.

来源:Hazardous Substances Data Bank (HSDB)

代谢

哺乳动物对多环芳烃的代谢会导致形成邻二醇环氧化合物（存在两种对映异构体和两种非对映异构体），如果环氧环位于母体碳氢化合物的湾区或峡湾区域，则被认为是重要的终极致癌物。在当前研究中，对湾区二醇环氧化合物的各种立体异构体进行了研究，包括屈曲、二苯并[a,h]-蒽和苯并[a]芘，以及峡湾区域的苯并[c]菲、苯并[c]屈曲和苯并[g]屈曲，这些与谷胱甘肽（GSH）在有人类谷胱甘肽S-转移酶同工酶GST A1-1存在或不存在的情况下进行孵化，GST A1-1是一种Alpha类酶。通过高效液相色谱（HPLC）确定并量化了GSH结合物的形成。结果表明，GST A1-1同工酶催化了所有测试的二醇环氧化合物形成GSH结合物，尽管观察到催化效率有显著差异（超过20倍）。对于湾区和峡湾区域的反式二醇环氧化合物，观察到对具有环氧环中苄基位置R配置的对映体进行结合的显著偏好。在峡湾区域二醇环氧化合物的同式非对映异构体中也注意到了类似的底物对映选择性，即具有相应R配置的对映体再次被优先结合。相比之下，对于湾区同式二醇环氧化合物，这种底物选择性被反转，导致对具有S配置的对映体的偏好。化学上更具活性的同式非对映异构体通常是GST A1-1的更好底物，而不是相应的反式非对映异构体。然而，不同二醇环氧化合物非对映异构体之间的比较并未发现化合物化学活性和催化效率之间的明显相关性。此外，二醇环氧化合物的亲脂性与催化效率之间也没有显著相关性。这表明立体化学因素，包括芳香环系统的尺寸和几何形状以及二醇环氧化合物的首选构象，是GST A1-1催化速率的主要决定因素。

Mammalian metabolism of polycyclic aromatic hydrocarbons results in the formation of vicinal diol epoxides (existing as enantiomeric pairs of two diastereomers) considered as important ultimate carcinogens if the oxirane ring is located in a bay or fjord region of the parent hydrocarbon. In the present study, individual stereoisomers of the bay region diol epoxides of chrysene, dibenz[a,h]-anthracene and benzo[a]pyrene, as well as of the fjord region diol epoxides of benzo[c]phenanthrene, benzo[c]chrysene and benzo[g]chrysene, have been incubated with glutathione (GSH) in the presence or absence of human glutathione S-transferase isoenzyme GST A1-1, a class Alpha enzyme. The formation of GSH conjugates was determined and quantified by HPLC. The results demonstrate that the GST A1-1 isoenzyme catalyzes the formation of GSH conjugates of all diol epoxides tested, although a marked variation in catalytic efficiency (>20-fold) was observed. With both bay and fjord region anti-diol epoxides a significant preference for conjugation of the enantiomer with the R configuration at the benzylic position of the oxirane ring was noted. Among the syn diastereomers of the fjord region diol epoxides a similar substrate enantioselectivity was noted, i.e. the enantiomer with the corresponding R configuration was again preferentially conjugated. In contrast, for the bay region syn-diol epoxides this substrate selectivity was reversed, resulting in a preference for the enantiomer with the S configuration. The chemically more reactive syn diastereomers were in general better substrates for GST A1-1 than the corresponding anti diastereomers. However, a comparison between different diol epoxide diastereomers revealed no obvious correlation between chemical reactivity of the compounds and catalytic efficiencies. Furthermore, no significant correlation between diol epoxide lipophilicity and catalytic efficiency was observed. It is suggested that stereochemical factors, including the size and the geometry of the aromatic ring system and the preferred conformation of the diol epoxide, are involved as the major determinant for the rate of catalysis by GST A1-1.

来源:Hazardous Substances Data Bank (HSDB)

毒理性

• 毒性总结

鉴定和使用：苯并(g)芘（B(g)C）是一种多环芳烃（PAH）。它不是商业生产的，主要用于生物化学研究。多环芳烃普遍存在于有机物燃烧产物中，包括香烟烟雾。人类暴露和毒性：在人类成纤维细胞中检测到四种主要的DNA加合物。动物研究：B(g)C是一种中等致癌物。B(g)C在小鼠皮肤中被代谢激活并形成DNA加合物。腺嘌呤加合物占B[g]C处理的小鼠皮肤中形成的总主要加合物的64%。B(g)C代谢物也在中国仓鼠V79细胞中形成DNA加合物。

IDENTIFICATION AND USE: Benzo(g)chrysene (B(g)C) is a polynuclear aromatic hydrocarbon (PAH). It is not produced commercially, and it is used mostly in biochemical research. PAHs are ubiquitous in combustion products of organic matter, including cigarette smoke. HUMAN EXPOSURE AND TOXICITY: Four major DNA adducts were detected in human fibroblasts. ANIMAL STUDIES: B(g)C is a moderate carcinogen. B(g)C is metabilically activated in mouse skin and forms DNA adducts. The adenine adducts accounted for 64% of the total major adducts formed in B[g]C-treated mouse skin. B(g)C metabolites formed also DNA adducts in Chinese hamster V79 cell.

来源:Hazardous Substances Data Bank (HSDB)

毒理性

• 致癌性证据

实验动物中关于苯并[g]芘致癌性的证据不足。苯并[g]芘对人类致癌性无法分类（第3组）。

There is inadequate evidence in experimental animals for the carcinogenicity of benzo[g]chrysene. Benzo[g]chrysene is not classifiable as to its carcinogenicity to humans (Group 3).

来源:Hazardous Substances Data Bank (HSDB)

毒理性

• 致癌物分类

国际癌症研究机构致癌物：苯并[g]芘

IARC Carcinogenic Agent:Benzo[g]chrysene

来源:International Agency for Research on Cancer (IARC)

毒理性

• 致癌物分类

国际癌症研究机构（IARC）致癌物分类：第3组：无法归类其对人类致癌性

IARC Carcinogenic Classes:Group 3: Not classifiable as to its carcinogenicity to humans

来源:International Agency for Research on Cancer (IARC)

毒理性

• 致癌物分类

国际癌症研究机构专著：第92卷：（2010年）一些非杂环多环芳烃及其相关暴露

IARC Monographs:Volume 92: (2010) Some Non-heterocyclic Polycyclic Aromatic Hydrocarbons and Some Related Exposures

来源:International Agency for Research on Cancer (IARC)

安全信息

• 海关编码：
  2902909090
• 储存条件：
  通风、低温、干燥

制备方法与用途

类别：有毒物品

可燃性危险特性：

• 可燃
• 燃烧时产生刺激烟雾

储运特性：

• 通风、低温、干燥

灭火剂：

• 干粉
• 泡沫
• 沙土
• 二氧化碳
• 雾状水

反应信息

• 作为反应物：
  描述：

  苯并[G]屈 在 lithium acetate 、 sodium methylate 、 N-溴代乙酰胺 作用下， 以 四氢呋喃 为溶剂， 反应 16.5h， 生成 1a,13c-Dihydrobenzo<11,12>chryseno<5,6-b>oxirene
  参考文献：
  名称：

  苯并[ g ] ch，苯并[ g ] ch9,10-氧化物和苯并[ g ] ry1,2,9：10-二氧化物的合成

  摘要：

  已经合成了苯并[ g ]苯并用于制备K区氧化烯，苯并[ g ]苯9,10-氧化物。合成峡湾区域的氧化芳烃苯并[ g ] 1,2,2-氧化物的尝试未成功，但已获得了峡湾区域的二芳烃氧化苯并[ g ] 1,2,9,10-二氧化物。

  DOI：

  10.1039/p19850000857
• 作为产物：
  描述：

  二苯并呋喃 在 2-双环己基膦-2',6'-二甲氧基联苯 、 吡啶 、 bis(1,5-cyclooctadiene)nickel (0) 、 tris-(dibenzylideneacetone)dipalladium(0) 、 C₂₃H₃₂N₂*ClH 、 potassium carbonate 作用下， 以 四氢呋喃 、 乙二醇二甲醚 、 二氯甲烷 为溶剂， 反应 48.0h， 生成 苯并[G]屈
  参考文献：
  名称：

  从镍催化的开环C-O芳基化反应开始，苯并呋喃从芳构型转变为三亚苯基

  摘要：

  已经开发出一类新的芳香族变态，其中二苯并呋喃被转化为三亚苯基。此转化过程由三个连续的操作组成：（1）镍催化的芳基溴化镁进行镍催化的开环C-O键芳基化；（2）所得的羟基部分与Tf 2 O的三氟甲磺酰化（triflation）；以及（3）钯-催化或光诱导的闭环。在最后的闭环步骤中，光诱导过程已证明比钯催化的过程生产力更高。通过使用π-延伸的二萘并呋喃作为底物，以令人满意的产率获得了背苯并稠合的[5]]烯。

  DOI：

  10.1021/acs.orglett.6b03861

文献信息

• Palladium-Catalyzed Cascade Dearomative Spirocyclization and C−H Annulation of Aromatic Halides with Alkynes
  作者：Xingrong Liao、Fulin Zhou、Zhengyang Bin、Yudong Yang、Jingsong You

  DOI：10.1021/acs.orglett.1c01736

  日期：2021.7.2

  Described herein is a palladium-catalyzed intermolecular dearomative annulation of aryl halides with alkynes, which provides a rapid approach to a class of structurally unique spiroembedded polycyclic aromatic compounds. The cascade process is accomplished by a sequential alkyne migratory insertion, Heck-type dearomatization, and C–H bond annulation. Further optoelectronic study indicated this fused

  本文描述的是钯催化的芳基卤化物与炔的分子间脱芳环化，这提供了一种快速制备一类结构独特的螺嵌入多环芳族化合物的方法。级联过程是通过连续的炔迁移插入、Heck 型脱芳构化和 C-H 键环化来完成的。进一步的光电研究表明，这种稠合螺环支架可能是 OLED 的潜在主体材料，例如最大外量子效率为 23.0% 的红色 PhOLED 器件。
• Two-in-One Strategy for the Pd(II)-Catalyzed Tandem C–H Arylation/Decarboxylative Annulation Involved with Cyclic Diaryliodonium Salts
  作者：Tao Hu、Kai Xu、Zenghui Ye、Kai Zhu、Yanqi Wu、Fengzhi Zhang

  DOI：10.1021/acs.orglett.9b02429

  日期：2019.9.20

  We report here a two-in-one strategy for the Pd(II)-catalyzed tandem C–H arylation/decarboxylative annulation between readily available cyclic diaryliodonium salts and benzoic acids. The carboxylic acid functionality can be used as both a directing group for the ortho-C–H arylation and the reactive group for the tandem decarboxylative annulation. By a step-economical double cross-coupling annulation

  我们在这里报告了一种二合一策略，用于在易于获得的环状二芳基碘鎓盐和苯甲酸之间进行Pd（II）催化的串联CH芳基化/脱羧环化反应。羧酸官能团既可以用作邻-C-H芳基化的直接基团，也可以用作串联脱羧环化的反应基团。通过分步经济的双交叉耦合环化程序，可以有效地构建特权的三亚苯基骨架，这在材料化学中具有潜在的应用。
• C–C Bond (Hetero)arylation of Ring-Fused Benzocyclobutenols and Application in the Assembly of Polycyclic Aromatic Hydrocarbons
  作者：Wenbin Mao、Chen Zhu

  DOI：10.1021/acs.joc.7b01727

  日期：2017.9.1

  efficient synthetic approach to triphenylene-based polycyclic aromatic hydrocarbons (PAHs) from ring-fused benzocyclobutenols (RBCBs) through the cleavage of the C–C σ-bond. Two key transformations are involved: (a) palladium-catalyzed C–C bond (hetero)arylation of RBCBs; and (b) Lewis acid-promoted intramolecular annulation leading to complex polycyclic compounds. A variety of multiply substituted triphenylenes

  在本文中，我们公开了一种新的，有效的合成方法，该方法通过裂解C–Cσ键，从环稠合的苯并环丁烯醇（RBCB）中合成基于三苯撑的多环芳烃（PAH）。涉及两个关键的转变：（a）RBCBs的钯催化C–C键（杂）芳基化；（b）路易斯酸促进的分子内环化反应，产生复杂的多环化合物。以合成上有用的产率获得了多种多取代的联苯撑及其衍生物。
• Palladium Catalyzed C–I and Vicinal C–H Dual Activation of Diaryliodonium Salts for Diarylations: Synthesis of Triphenylenes
  作者：Xunshen Wu、Jianwei Han、Limin Wang

  DOI：10.1021/acs.joc.7b01905

  日期：2018.1.5

  we report an approach for direct diarylations of 2-bromobiphenyls or bromobenzenes. As a result, a wide range of triphenylenes with various substituents have been synthesized in good yields. These triphenylenes are expected to be employed in the “bottom-up” synthesis of functional aromatic molecules in material science.

  使用钯催化二芳基碘鎓盐的C–I和邻位C–H键的双重活化的合成策略，我们报道了一种用于2-溴代联苯或溴苯直接二芳基化的方法。结果，已经以良好的产率合成了范围广泛的具有各种取代基的三亚苯基。这些三亚苯基有望在材料科学中用于功能性芳族分子的“自下而上”合成。
• Palladium-Assisted “Aromatic Metamorphosis” of Dibenzothiophenes into Triphenylenes
  作者：Dhananjayan Vasu、Hideki Yorimitsu、Atsuhiro Osuka

  DOI：10.1002/anie.201501992

  日期：2015.6.8

  Two new palladium‐catalyzed reactions of aromatic sulfur compounds enabled the conversion of dibenzothiophenes into triphenylenes in four steps. This transformation of one aromatic framework into another consists of 1) 4‐chlorobutylation of the dibenzothiophene to form the corresponding sulfonium salt, 2) palladium‐catalyzed arylative ring opening of the sulfonium salt with a sodium tetraarylborate

  芳香族硫化合物的两个新的钯催化反应使二苯并噻吩在四个步骤中转化为苯并菲。一种芳族骨架向另一种芳族骨架的转化包括：1）二苯并噻吩的4-氯丁基化反应形成相应的sulf盐； 2）钯盐与四芳基硼酸钠的钯催化的芳基开环反应； 3）分子内S N 2反应以形成teraryl锍盐，和4）的钯催化的分子内ç  S / C  H至电palladation耦合。以量身定制的方式合成了所需的对称和不对称的三亚苯基，其总收率令人满意。